QQ: avoid dead lock in queue federation.

When processing the queue federation startup even the process
may call back into the ra process causing a deadlock. in this
case we spawn a temporary process to avoid this.

Author: kjnilsson

deps/rabbit/src/rabbit_quorum_queue.erl

@@ -547,6 +547,10 @@ spawn_deleter(QName) ->
                   delete(Q, false, false, <<"expired">>)
           end).
 
+spawn_notify_decorators(QName, startup = Fun, Args) ->
+    spawn(fun() ->
+                  notify_decorators(QName, Fun, Args)
+          end);
 spawn_notify_decorators(QName, Fun, Args) ->
     %% run in ra process for now
     catch notify_decorators(QName, Fun, Args).