UserTransaction rollback trips over null pointer and generates inappropriate error

The WS-AT remote UserTransactionImple rollback method fails to detect the case where there is no TX associated with the calling thread and trips over the resulting null pointer generating an invalid error code. This problem appears in both 1.0 and 1.1 implementations and also affects methods in the WS-BA UserBusinessActivityImple class.

This should be fixed by checking for null and explicitly throwing a WrongStateException which needs to be added to the parent API class. This is as near as possible to the JTA behaviour where an IllegalStateException is thrown.