samples: IoT MQTT Tests (#966)

* Adds MQTT device tests and example of configuration retrieval

* Fixes compilation

* Changes RSA certs to not expire, updates manager with setConfig, adds tests.

* Updates MQTT client dependency to use latest version from Maven central.

* Removes unused scripts and updates sample quickstart instructions.

* Updates flaky tests in vision beta.

vision/snippets/src/test/java/com/example/vision/DetectIT.java

@@ -283,7 +283,8 @@ public void testDetectWebEntitiesIncludeGeoResults() throws Exception {
 
     // Assert
     String got = bout.toString();
-    assertThat(got).contains("Zepra");
+    // Note: entities and labels can change over time.
+    assertThat(got).contains("Tel Aviv");
   }
 
   @Test