fix(cth-suite): use cheaper check for loaded applications

apps/emqx/test/emqx_cth_suite.erl

@@ -177,10 +177,9 @@ load_appspec({App, _Opts}) ->
     load_app_deps(App).
 
 load_app_deps(App) ->
-    AlreadyLoaded = [A || {A, _, _} <- application:loaded_applications()],
     case application:get_key(App, applications) of
         {ok, Deps} ->
-            Apps = Deps -- AlreadyLoaded,
+            Apps = [D || D <- Deps, application:get_key(D, id) == undefined],
             ok = lists:foreach(fun emqx_common_test_helpers:load/1, Apps),
             ok = lists:foreach(fun load_app_deps/1, Apps);
         undefined ->