pr comment changes and add synchronized to wasControlAcquired()

Author: sbSteveK

src/main/java/software/amazon/awssdk/crt/mqtt5/Mqtt5PublishAcknowledgementControlHandle.java

@@ -15,7 +15,7 @@ public class Mqtt5PublishAcknowledgementControlHandle {
     private final long controlId;
 
     /**
-     * Creates a new Mqtt5PublishAcknowledgementControlHandle. Only called from native/JNI code.
+     * Creates a new Mqtt5PublishAcknowledgementControlHandle.
      *
      * @param controlId The native publish acknowledgement control ID returned by
      *                  aws_mqtt5_client_acquire_publish_acknowledgement.
@@ -25,7 +25,9 @@ public class Mqtt5PublishAcknowledgementControlHandle {
     }
 
     /**
-     * Returns the native publish acknowledgement control ID. Used internally by JNI.
+     * Returns the native publish acknowledgement control ID, used by
+     * {@link Mqtt5Client#invokePublishAcknowledgement(Mqtt5PublishAcknowledgementControlHandle)}
+     * to pass the control ID to native code.
      *
      * @return The native publish acknowledgement control ID.
      */

src/main/java/software/amazon/awssdk/crt/mqtt5/PublishReturn.java

@@ -82,7 +82,7 @@ public synchronized Mqtt5PublishAcknowledgementControlHandle acquirePublishAckno
      *
      * @return {@code true} if the user acquired manual control of the PUBACK, {@code false} otherwise.
      */
-    private boolean wasControlAcquired() {
+    private synchronized boolean wasControlAcquired() {
         return controlAcquired;
     }