MQTT auth_SUITE: synchronise concurrent setup with the test

(cherry picked from commit e8fccba)

Author: michaelklishin

deps/rabbitmq_mqtt/test/auth_SUITE.erl

@@ -396,11 +396,17 @@ client_id_propagation(Config) ->
                                                              rabbit_auth_backend_mqtt_mock),
     %% setup creates the ETS table required for the mqtt auth mock
     %% it blocks indefinitely so we need to spawn
+    Self = self(),
     _ = spawn(fun () ->
                       rabbit_ct_broker_helpers:rpc(Config, 0, rabbit_auth_backend_mqtt_mock,
                                                    setup,
-                                                   [])
+                                                   [Self])
               end),
+    %% the setup process will notify us
+    receive
+        ok         -> ok
+        after 3000 -> ok
+    end,
     ClientId = <<"client-id-propagation">>,
     {ok, C} = connect_user(<<"client-id-propagation">>, <<"client-id-propagation">>,
                            Config, ClientId),

deps/rabbitmq_mqtt/test/rabbit_auth_backend_mqtt_mock.erl

@@ -13,14 +13,15 @@
 -behaviour(rabbit_authn_backend).
 -behaviour(rabbit_authz_backend).
 
--export([setup/0,
+-export([setup/1,
          user_login_authentication/2, user_login_authorization/2,
          check_vhost_access/3, check_resource_access/4, check_topic_access/4,
          state_can_expire/0,
          get/1]).
 
-setup() ->
+setup(CallerPid) ->
     ets:new(?MODULE, [set, public, named_table]),
+    CallerPid ! ok,
     receive
         stop -> ok
     end.