This patch tries to a fix a race in the session saving and shutdown code of ksmserver.
The race may happen on wmPhase1WaitingCount variable when WM-type clients are fast enough to complete their save requests while the loop in KSMServer::shutdown is still iterating.  As a result wmPhase1WaitingCount may become zero too early and that would kick off the next save/shutdown phase in a client's callback.  In fact, it might even go multiple times from zero to non-zero and back during the WM-specific loop.