WFLY-3548 Correct jndi namespace selection for synchronization callback ...

...served by corba threads

Add JTSSynchronizationWrapper to WeldTransactionServices class. This wrapper stores NamespaceContextSelector which is on the top of selector stack when synchronization object is created and pushes it on the top off the stack whenever synchronization callback is executed. This enables synchronization callbacks handled by corba threads to work correctly. Synchronization objects are wrapped only if jts is enabled in server configuration to avoid perfoming this operation in non-jts environments when it is never necessary.