fix: only set default for max_conn_rate and update test case

This revert the change in commit e291dcd for all listener "short
path fields" except the field max_conn_rate so they no longer have a
default value. It also updates a test case that assume that no listener
config is created by default but this is no longer the case when there
is a default value for the max_conn_rate field.

apps/emqx/src/emqx_limiter/src/emqx_limiter_schema.erl

@@ -212,17 +212,29 @@ short_paths_fields() ->
 short_paths_fields(Importance) ->
     [
         {Name,
-            ?HOCON(rate_type(), #{
+            ?HOCON(
+                rate_type(),
+                maps:merge(
+                    #{
                         desc => ?DESC(Name),
                         required => false,
-                default => infinity,
                         importance => Importance,
                         example => Example
-            })}
+                    },
+                    short_paths_fields_extra(Name)
+                )
+            )}
      || {Name, Example} <-
             lists:zip(short_paths(), [<<"1000/s">>, <<"1000/s">>, <<"100MB/s">>])
     ].
 
+short_paths_fields_extra(max_conn_rate) ->
+    #{
+        default => infinity
+    };
+short_paths_fields_extra(_Name) ->
+    #{}.
+
 desc(limiter) ->
     "Settings for the rate limiter.";
 desc(node_opts) ->

apps/emqx/test/emqx_ratelimiter_SUITE.erl

@@ -816,8 +816,8 @@ t_no_limiter_for_listener(_) ->
     CfgStr = <<>>,
     ok = emqx_common_test_helpers:load_config(emqx_schema, CfgStr),
     ListenerOpt = emqx:get_config([listeners, tcp, default]),
-    ?assertEqual(
-        undefined,
+    ?assertMatch(
+        #{connection := #{rate := infinity}},
         emqx_limiter_utils:get_listener_opts(ListenerOpt)
     ).