BUG/MINOR: haproxy: don't wake already stopping threads on exit

Commit d645574 ("MINOR: soft-stop: let the first stopper only signal
other threads") introduced a minor mistake which is that when a stopping
thread signals all other threads, it also signals itself. When
single-threaded, the process constantly wakes up while waiting for
last connections to exit. Let's reintroduce the lost mask to avoid
this.

No backport is needed, this is 2.2-dev only.

src/haproxy.c

@@ -2926,7 +2926,7 @@ void run_poll_loop()
 				if (_HA_ATOMIC_OR(&stopping_thread_mask, tid_bit) == tid_bit) {
 					/* notify all threads that stopping was just set */
 					for (i = 0; i < global.nbthread; i++)
-						if ((all_threads_mask >> i) & 1)
+						if (((all_threads_mask & ~stopping_thread_mask) >> i) & 1)
 							wake_thread(i);
 				}
 			}