Fix an issue of failing to recreate a requestresponse opener object in case of connection failures (#446)

Author: sjkwak

azure-eventhubs/src/main/java/com/microsoft/azure/eventhubs/impl/RequestResponseOpener.java

@@ -103,6 +103,8 @@ public void onError(Exception error) {
                         eventDispatcher.deregisterForConnectionError(requestResponseChannel.getSendLink());
                         eventDispatcher.deregisterForConnectionError(requestResponseChannel.getReceiveLink());
 
+                        isOpened = false;
+
                         if (TRACE_LOGGER.isWarnEnabled()) {
                             TRACE_LOGGER.warn(String.format(Locale.US, "requestResponseChannel.onClose error clientId[%s], session[%s], link[%s], endpoint[%s], error %s",
                                     clientId, sessionName, linkName, endpointAddress, error));