msg/async: fix accept_conn not remove entry in conns when lazy delete

Signed-off-by: Haomai Wang <haomai@xsky.com>

src/msg/async/AsyncMessenger.h

@@ -353,6 +353,8 @@ public:
       // If conn already in, we will return 0
       Mutex::Locker l(deleted_lock);
       if (deleted_conns.erase(existing)) {
+        existing->get_perf_counter()->dec(l_msgr_active_connections);
+        conns.erase(it);
       } else if (conn != existing) {
         return -1;
       }