fixup! Fix Cowboy crashes caused by double reply

Author: lhoguin

deps/rabbitmq_management/src/rabbit_mgmt_wm_exchange_publish.erl

@@ -30,7 +30,7 @@ content_types_provided(ReqData, Context) ->
    {rabbit_mgmt_util:responder_map(to_json), ReqData, Context}.
 
 resource_exists(ReqData, Context) ->
-    case rabbit_mgmt_wm_queue:exchange(ReqData) of
+    case rabbit_mgmt_wm_exchange:exchange(ReqData) of
         not_found -> {false, set_resp_not_found(ReqData), Context};
         _         -> {true, ReqData, Context}
     end.