Fix flaky test on windows

Windows github machines are flaky, and running hostname on them
sometimes returns short name, sometimes fqdn. Not sure what is the
cause. Workaround is to ignore results from `hostname' which do not have
`.' in them.

fqdn_test.go

@@ -42,16 +42,16 @@ func TestFromLookup(t *testing.T) {
 	for _, tc := range testCases {
 		fqdn, err := fromLookup(tc.host)
 		if !errors.Is(err, tc.err) {
-			t.Fatalf("Unexpected error.\n"+
+			t.Fatalf("Unexpected error (%q).\n"+
 				"\tExpected: %T\n"+
 				"\tActual  : %T\n",
-				tc.err, err)
+				tc.host, tc.err, err)
 		}
 		if fqdn != tc.fqdn {
-			t.Fatalf("Fqdn does not match.\n"+
+			t.Fatalf("Fqdn does not match (%q).\n"+
 				"\tExpected: %q\n"+
 				"\tActual  : %q\n",
-				tc.fqdn, fqdn)
+				tc.host, tc.fqdn, fqdn)
 		}
 	}
 }
@@ -100,6 +100,14 @@ func TestMatchHostname(t *testing.T) {
 	outS = strings.ToLower(outS)
 	fqdn = strings.ToLower(fqdn)
 
+	// Windows github machines are flaky, and running hostname on them
+	// sometimes returns short name, sometimes fqdn. Not sure what is the
+	// cause. Workaround is to ignore results from the system which do not
+	// have `.' in them.
+	if !strings.ContainsRune(outS, '.') {
+		return
+	}
+
 	if outS != fqdn {
 		t.Fatalf("Output from hostname does not match.\n"+
 			"\tUs  : %q\n"+