amqp_client_SUITE: Load test module on broker before using one of its anonymous functions

[Why]
Before this change, when the `idle_time_out_on_server/1` test case was runned first in the
shuffled test group, the test module was not loaded on the remote broker.
When the anonymous function was passed to meck and was executed, we got
the following crash on the broker:

    crasher:
      initial call: rabbit_heartbeat:'-heartbeater/2-fun-0-'/0
      pid: <0.704.0>
      registered_name: []
      exception error: {undef,
                           [{#Fun<amqp_client_SUITE.14.116163631>,
                             [#Port<0.45>,[recv_oct]],
                             []},
                            {rabbit_heartbeat,get_sock_stats,3,
                                [{file,"rabbit_heartbeat.erl"},{line,175}]},
                            {rabbit_heartbeat,heartbeater,3,
                                [{file,"rabbit_heartbeat.erl"},{line,155}]},
                            {proc_lib,init_p,3,
                                [{file,"proc_lib.erl"},{line,317}]},
                            {rabbit_net,getstat,[#Port<0.45>,[recv_oct]],[]}]}

This led to a failure of the test case later, when it waited for a
message from the connecrtion.

We do the same in two other test cases where this is likely to happen
too.

[How]
Loading the module first fixes the problem.

Author: dumbbell

deps/rabbit/test/amqp_client_SUITE.erl

@@ -1867,6 +1867,11 @@ link_target_queue_deleted(QType, Config) ->
     ok = amqp10_client:send_msg(Sender, amqp10_msg:new(DTag1, <<"m1">>, false)),
     ok = wait_for_accepted(DTag1),
 
+    %% Load test module on the broker: we reference an anonymous function
+    %% from it during the configuration of meck.
+    [_ | _] = rabbit_ct_broker_helpers:rpc(
+                Config, ?MODULE, module_info, []),
+
     %% Mock delivery to the target queue to do nothing.
     rabbit_ct_broker_helpers:setup_meck(Config, [?MODULE]),
     Mod = rabbit_queue_type,
@@ -1927,6 +1932,11 @@ target_queues_deleted_accepted(Config) ->
     ok = amqp10_client:send_msg(Sender, amqp10_msg:new(DTag1, <<"m1">>, false)),
     ok = wait_for_accepted(DTag1),
 
+    %% Load test module on the broker: we reference an anonymous function
+    %% from it during the configuration of meck.
+    [_ | _] = rabbit_ct_broker_helpers:rpc(
+                Config, ?MODULE, module_info, []),
+
     %% Mock to deliver only to q1.
     rabbit_ct_broker_helpers:setup_meck(Config, [?MODULE]),
     Mod = rabbit_queue_type,
@@ -4726,6 +4736,11 @@ idle_time_out_on_server(Config) ->
         after 30000 -> ct:fail({missing_event, ?LINE})
         end,
 
+        %% Load test module on the broker: we reference an anonymous function
+        %% from it during the configuration of meck.
+        [_ | _] = rabbit_ct_broker_helpers:rpc(
+                    Config, ?MODULE, module_info, []),
+
         %% Mock the server socket to not have received any bytes.
         rabbit_ct_broker_helpers:setup_meck(Config),
         ok = rpc(Config, meck, new, [Mod, [no_link, passthrough]]),