Fixing racing condition on listen socket close in router.

Listen socket is actually closed in the instant timer handler.  This patch moves
the "configuration has been applied" notification to the timer handler to avoid
a situation when the user gets the response from the controller, but the listen
socket is still open in the router.

src/nxt_router.h

@@ -205,6 +205,8 @@ typedef struct {
     nxt_event_engine_t     *engine;
     nxt_socket_conf_t      *socket_conf;
 
+    nxt_joint_job_t        *close_job;
+
     nxt_upstream_t         **upstreams;
 
     /* Modules configuraitons. */