[WINSRV] Wait for the process to exit after calling NtTerminateProcess

NtTerminateProcess just queues an apc in every thread of the target process which in turn kills each thread. We need to wait so that all processes have enough time to exit before shutting down.

win32ss/user/winsrv/usersrv/shutdown.c

@@ -796,6 +796,8 @@ UserClientShutdown(IN PCSR_PROCESS CsrProcess,
 #endif
     NtTerminateProcess(CsrProcess->ProcessHandle, 0);
 
+    WaitForSingleObject(CsrProcess->ProcessHandle, ShutdownSettings.ProcessTerminateTimeout);
+
     /* We are done */
     CsrDereferenceProcess(CsrProcess);
     return CsrShutdownCsrProcess;