BUG/MEDIUM: queues: Adjust the proxy counters when appropriate

In process_srv_queue(), if we manage to successfully run an extra task,
don't forget to adjust the proxy's totpend and served counters accordingly.
Having an inaccurate served could lead to various subtle bugs, as it is
used when making load balancing decisions.

This should not be backported, unless cda7275
is backported too.

src/queue.c

@@ -452,8 +452,11 @@ int process_srv_queue(struct server *s)
 		 * checked, but before we set ready_srv so it would not see it,
 		 * just in case try to run one more stream.
 		 */
-		if (pendconn_process_next_strm(s, p, px_ok))
+		if (pendconn_process_next_strm(s, p, px_ok)) {
+			_HA_ATOMIC_SUB(&p->totpend, 1);
+			_HA_ATOMIC_ADD(&p->served, 1);
 			done++;
+		}
 	}
 	return done;
 }