rabbit_peer_discovery: Always execute teardown code after exception

[Why]
We start a temporary hidden node, then ask it to execute some code, then
stop it. But if there is an execution in between, we leave the
temporary hidden node running.

Likewise when we mess with the group leader: if the function executed
after overriding the group leader temporarily raises an exception, the
group leader becomes permanent and we may miss log messages.

[How]
We simply use a try/after block to ensure the temporary things are
reverted at the end, regardless of the success or failure.

Follow up to #9797.

Submitted by: @lukebakken

Author: dumbbell

deps/rabbit/src/rabbit_peer_discovery.erl

@@ -387,9 +387,11 @@ query_node_props(Nodes) when Nodes =/= [] ->
                "discovered peers properties",
                [Peer],
                #{domain => ?RMQLOG_DOMAIN_PEER_DISC}),
-            Ret = erpc:call(Peer, ?MODULE, do_query_node_props, [Nodes]),
-            peer:stop(Pid),
-            Ret;
+            try
+                erpc:call(Peer, ?MODULE, do_query_node_props, [Nodes])
+            after
+                peer:stop(Pid)
+            end;
         {error, _} = Error ->
             ?LOG_ERROR(
                "Peer discovery: failed to start temporary hidden node to "
@@ -448,10 +450,12 @@ do_query_node_props(Nodes) when Nodes =/= [] ->
 
 with_group_leader_proxy(ProxyGroupLeader, Fun) ->
     UpstreamGroupLeader = erlang:group_leader(),
-    true = erlang:group_leader(ProxyGroupLeader, self()),
-    Ret = Fun(),
-    true = erlang:group_leader(UpstreamGroupLeader, self()),
-    Ret.
+    try
+        true = erlang:group_leader(ProxyGroupLeader, self()),
+        Fun()
+    after
+              true = erlang:group_leader(UpstreamGroupLeader, self())
+    end.
 
 group_leader_proxy(Parent, UpstreamGroupLeader) ->
     receive