fix(Auth): prevent multiple invocations of success callback for updateUserAttributes (#1339)

Author: Jordan-Nelson

aws-auth-cognito/src/main/java/com/amplifyframework/auth/cognito/AWSCognitoAuthPlugin.java

@@ -849,8 +849,8 @@ public void onResult(List<UserCodeDeliveryDetails> result) {
                                                         null)
                                         ));
                             }
-                            onSuccess.accept(resultMap);
                         }
+                        onSuccess.accept(resultMap);
                     }
 
                     @Override

testutils/src/main/java/com/amplifyframework/testutils/Await.java

@@ -140,6 +140,9 @@ private static <R, E extends Throwable> void await(
             try {
                 resultErrorEmitter.emitTo(
                     result -> {
+                        if (resultContainer.get() != null) {
+                            throw new RuntimeException("Result callback called more than once with result: " + result);
+                        }
                         resultContainer.set(result);
                         latch.countDown();
                     }, error -> {