QQ: force delete followers after leader has terminated.

In some mixed machine version scenarios some followers will never
apply the poison pill command so we may as well force delete them
just in case.

Author: Karl Nilsson

deps/rabbit/src/rabbit_quorum_queue.erl

@@ -736,6 +736,9 @@ delete(Q, _IfUnused, _IfEmpty, ActingUser) when ?amqqueue_is_quorum(Q) ->
             MRef = erlang:monitor(process, Leader),
             receive
                 {'DOWN', MRef, process, _, _} ->
+                    %% leader is down,
+                    %% force delete remaining members
+                    ok = force_delete_queue(lists:delete(Leader, Servers)),
                     ok
             after Timeout ->
                     erlang:demonitor(MRef, [flush]),