test: add a 2 seconds sleep between listener sotp and restart

to lower the chance of eaddrinuse

apps/emqx/test/emqx_listeners_SUITE.erl

@@ -133,6 +133,8 @@ t_start_stop_listeners(_) ->
 t_restart_listeners(_) ->
     ok = emqx_listeners:start(),
     ok = emqx_listeners:stop(),
+    %% flakyness: eaddrinuse
+    timer:sleep(timer:seconds(2)),
     ok = emqx_listeners:restart(),
     ok = emqx_listeners:stop().