Release unnecessary references to reduce memory usage as soon as called onComplete()

Author: Hideki Itakura

src/main/java/com/couchbase/lite/support/RemoteRequestRetry.java

@@ -185,15 +185,20 @@ private RemoteRequest generateRemoteRequest() {
         return request;
     }
 
-
     RemoteRequestCompletionBlock onCompletionInner = new RemoteRequestCompletionBlock() {
 
         private void completed(HttpResponse httpResponse, Object result, Throwable e) {
             requestHttpResponse = httpResponse;
             requestResult = result;
             requestThrowable = e;
             completedSuccessfully.set(true);
+
             onCompletionCaller.onCompletion(requestHttpResponse, requestResult, requestThrowable);
+
+            // release unnecessary references to reduce memory usage as soon as called onComplete().
+            requestHttpResponse = null;
+            requestResult = null;
+            requestThrowable = null;
         }
 
         @Override