PT-42880563: When timer C fires and an INVITE transaction is already within or beyond the COMPLETED state, touch() method is still invoked. This results to the transaction lifetime getting reset. The current lifetime is 5 minutes. having timer C reset this doubles the transaction lifetime to 10 minutes. This can be normally interpreted as leak. However, this is just a case of delayed garbage collection. This patch corrects this from ever occuring.
PT-42880563: The timer user data can be deted in SipUserAgent::handleMessage and in the tansaciton constructor.  During heavy retransmision, a race condition may occur with the garbage collector and the message queue leading to the user data not getting deleted.  This seldom happens but accumulates as a permanent leak overtime.