Fix cancellation of real time queries

Without this change multi_real_time_transaction blocks forever (on
Windows) in the block where it repeatedly calls pg_advisory_lock(15).
This happens because the deadlock detector tries to cancel the backend
but the backend never processes that signal.

src/backend/distributed/executor/multi_real_time_executor.c

@@ -199,6 +199,16 @@ MultiRealTimeExecute(Job *job)
 		{
 			MultiClientWait(waitInfo);
 		}
+
+#ifdef WIN32
+
+		/*
+		 * Don't call CHECK_FOR_INTERRUPTS because we want to clean up after ourselves,
+		 * calling pgwin32_dispatch_queued_signals sets QueryCancelPending so we leave
+		 * the loop.
+		 */
+		pgwin32_dispatch_queued_signals();
+#endif
 	}
 
 	MultiClientFreeWaitInfo(waitInfo);