MCOL-529 Pool DBRM connections

DBRM connections are reused so that we don't have a huge amount of
TIME_WAIT sockets when there are large amounts of DML. Also applied to
i_s.columnstore_files

utils/messageqcpp/messagequeue.h

@@ -249,6 +249,9 @@ public:
 	 */
 	inline const bool isSameAddr(const MessageQueueClient& rhs) const;
 
+    bool isConnected() { return fClientSock.isConnected(); }
+    
+    bool hasData() { return fClientSock.hasData(); }
 	/*
 	 * allow test suite access to private data for OOB test
 	 */