Use TAR instead of DOCKER build type before 6.7.0 (#40723)

In 6.7.0 (#39378) we added a build type of DOCKER for the docker images, but
unfortunately earlier versions do not understand this and will reject any
transport messages that mention this build type.

This commit fixes this by reporting TAR instead of DOCKER when talking to older
nodes.

Relates (but does not fix) #40511
Relates #39378

This commit is the changes that were supposed to be included in the preceding
one, abe509a, but weren't because of a missing
`git add`.

server/src/test/java/org/elasticsearch/BuildTests.java

@@ -115,65 +115,52 @@ private static String randomStringExcept(final String s) {
     public void testSerialization() {
         EqualsHashCodeTestUtils.checkEqualsAndHashCode(new WriteableBuild(new Build(
                 randomFrom(Build.Flavor.values()), randomFrom(Build.Type.values()),
-                randomAlphaOfLength(6), randomAlphaOfLength(6), randomBoolean(), randomAlphaOfLength(6))),
+                randomAlphaOfLength(6), randomAlphaOfLength(6), randomBoolean())),
             b -> copyWriteable(b, writableRegistry(), WriteableBuild::new, Version.CURRENT),
             b -> {
-                switch (randomIntBetween(1, 6)) {
+                switch (randomIntBetween(1, 5)) {
                     case 1:
                         return new WriteableBuild(new Build(
                             randomValueOtherThan(b.build.flavor(), () -> randomFrom(Build.Flavor.values())), b.build.type(),
-                            b.build.shortHash(), b.build.date(), b.build.isSnapshot(), b.build.getQualifiedVersion()));
+                            b.build.shortHash(), b.build.date(), b.build.isSnapshot()));
                     case 2:
                         return new WriteableBuild(new Build(b.build.flavor(),
                             randomValueOtherThan(b.build.type(), () -> randomFrom(Build.Type.values())),
-                            b.build.shortHash(), b.build.date(), b.build.isSnapshot(), b.build.getQualifiedVersion()));
+                            b.build.shortHash(), b.build.date(), b.build.isSnapshot()));
                     case 3:
                         return new WriteableBuild(new Build(b.build.flavor(), b.build.type(),
-                            randomStringExcept(b.build.shortHash()), b.build.date(), b.build.isSnapshot(), b.build.getQualifiedVersion()));
+                            randomStringExcept(b.build.shortHash()), b.build.date(), b.build.isSnapshot()));
                     case 4:
                         return new WriteableBuild(new Build(b.build.flavor(), b.build.type(),
-                            b.build.shortHash(), randomStringExcept(b.build.date()), b.build.isSnapshot(), b.build.getQualifiedVersion()));
+                            b.build.shortHash(), randomStringExcept(b.build.date()), b.build.isSnapshot()));
                     case 5:
                         return new WriteableBuild(new Build(b.build.flavor(), b.build.type(),
-                            b.build.shortHash(), b.build.date(), b.build.isSnapshot() == false, b.build.getQualifiedVersion()));
-                    case 6:
-                        return new WriteableBuild(new Build(b.build.flavor(), b.build.type(),
-                            b.build.shortHash(), b.build.date(), b.build.isSnapshot(), randomStringExcept(b.build.getQualifiedVersion())));
+                            b.build.shortHash(), b.build.date(), b.build.isSnapshot() == false));
                 }
                 throw new AssertionError();
             });
     }
 
     public void testSerializationBWC() throws IOException {
         final WriteableBuild dockerBuild = new WriteableBuild(new Build(randomFrom(Build.Flavor.values()), Build.Type.DOCKER,
-            randomAlphaOfLength(6), randomAlphaOfLength(6), randomBoolean(), randomAlphaOfLength(6)));
+            randomAlphaOfLength(6), randomAlphaOfLength(6), randomBoolean()));
 
         final List<Version> versions = Version.getDeclaredVersions(Version.class);
         final Version pre63Version = randomFrom(versions.stream().filter(v -> v.before(Version.V_6_3_0)).collect(Collectors.toList()));
         final Version post63Pre67Version = randomFrom(versions.stream()
             .filter(v -> v.onOrAfter(Version.V_6_3_0) && v.before(Version.V_6_7_0)).collect(Collectors.toList()));
-        final Version post67Pre70Version = randomFrom(versions.stream()
-            .filter(v -> v.onOrAfter(Version.V_6_7_0) && v.before(Version.V_7_0_0)).collect(Collectors.toList()));
-        final Version post70Version = randomFrom(versions.stream().filter(v -> v.onOrAfter(Version.V_7_0_0)).collect(Collectors.toList()));
+        final Version post67Version = randomFrom(versions.stream().filter(v -> v.onOrAfter(Version.V_6_7_0)).collect(Collectors.toList()));
 
         final WriteableBuild pre63 = copyWriteable(dockerBuild, writableRegistry(), WriteableBuild::new, pre63Version);
         final WriteableBuild post63pre67 = copyWriteable(dockerBuild, writableRegistry(), WriteableBuild::new, post63Pre67Version);
-        final WriteableBuild post67pre70 = copyWriteable(dockerBuild, writableRegistry(), WriteableBuild::new, post67Pre70Version);
-        final WriteableBuild post70 = copyWriteable(dockerBuild, writableRegistry(), WriteableBuild::new, post70Version);
+        final WriteableBuild post67 = copyWriteable(dockerBuild, writableRegistry(), WriteableBuild::new, post67Version);
 
         assertThat(pre63.build.flavor(), equalTo(Build.Flavor.OSS));
         assertThat(post63pre67.build.flavor(), equalTo(dockerBuild.build.flavor()));
-        assertThat(post67pre70.build.flavor(), equalTo(dockerBuild.build.flavor()));
-        assertThat(post70.build.flavor(), equalTo(dockerBuild.build.flavor()));
+        assertThat(post67.build.flavor(), equalTo(dockerBuild.build.flavor()));
 
         assertThat(pre63.build.type(), equalTo(Build.Type.UNKNOWN));
         assertThat(post63pre67.build.type(), equalTo(Build.Type.TAR));
-        assertThat(post67pre70.build.type(), equalTo(dockerBuild.build.type()));
-        assertThat(post70.build.type(), equalTo(dockerBuild.build.type()));
-
-        assertThat(pre63.build.getQualifiedVersion(), equalTo(pre63Version.toString()));
-        assertThat(post63pre67.build.getQualifiedVersion(), equalTo(post63Pre67Version.toString()));
-        assertThat(post67pre70.build.getQualifiedVersion(), equalTo(post67Pre70Version.toString()));
-        assertThat(post70.build.getQualifiedVersion(), equalTo(dockerBuild.build.getQualifiedVersion()));
+        assertThat(post67.build.type(), equalTo(dockerBuild.build.type()));
     }
 }