Check for breakout condition in timer callback

Change-Id: I357cfd3e6cf907d4e8858bee0f052bf9fdc467d0
Reviewed-on: http://review.couchbase.org/18542
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>

src/timer.c

@@ -28,6 +28,7 @@ static void timer_callback(libcouchbase_socket_t sock,
         instance->io->delete_timer(instance->io, timer->event);
         libcouchbase_timer_destroy(instance, timer);
     }
+    libcouchbase_maybe_breakout(timer->instance);
 
     (void)sock;
     (void)which;