fix(emqx): avoid interference in testsuites

Also remove that `?wait_async_action` in `emqx_trace_SUITE` which
consistently becomes stuck for 100 seconds. It's not clear why it
was there in the first place because listeners should start
synchronously, so `emqx_common_test_helpers:start_apps/1` won't return
until required listeners are started.

apps/emqx/test/emqx_common_test_helpers.erl

@@ -347,6 +347,7 @@ stop_apps(Apps, Opts) ->
     ok = mria_mnesia:delete_schema(),
     %% to avoid inter-suite flakiness
     application:unset_env(emqx, init_config_load_done),
+    application:unset_env(emqx, boot_modules),
     persistent_term:erase(?EMQX_AUTHENTICATION_SCHEMA_MODULE_PT_KEY),
     case Opts of
         #{erase_all_configs := false} ->

apps/emqx/test/emqx_tls_certfile_gc_SUITE.erl

@@ -326,8 +326,7 @@ t_gc_active(_Config) ->
             emqx_tls_certfile_gc:run()
         )
     after
-        emqx_common_test_helpers:stop_apps([]),
-        emqx_common_test_helpers:boot_modules(all)
+        emqx_common_test_helpers:stop_apps([])
     end.
 
 orphans() ->

apps/emqx/test/emqx_trace_SUITE.erl

@@ -33,21 +33,12 @@ all() ->
     emqx_common_test_helpers:all(?MODULE).
 
 init_per_suite(Config) ->
-    %% ensure dependent apps stopped
-    emqx_common_test_helpers:stop_apps([]),
-    ?check_trace(
-        ?wait_async_action(
-            emqx_common_test_helpers:start_apps([]),
-            #{?snk_kind := listener_started, bind := 1883},
-            timer:seconds(100)
-        ),
-        fun(Trace) ->
-            ct:pal("listener start statuses: ~p", [
-                ?of_kind([listener_started, listener_not_started], Trace)
-            ]),
-            %% more than one listener
-            ?assertMatch([_ | _], ?of_kind(listener_started, Trace))
-        end
+    ok = emqx_common_test_helpers:start_apps([]),
+    Listeners = emqx_listeners:list(),
+    ct:pal("emqx_listeners:list() = ~p~n", [Listeners]),
+    ?assertMatch(
+        [_ | _],
+        [ID || {ID, #{running := true}} <- Listeners]
     ),
     Config.