rabbit_vhost:delete/2: Return no_such_vhost when the vhost isn't deleted

Previously `rabbit_vhost:delete/2` threw this error within
`rabbit_policy:list/2` when the vhost didn't exist. We can return the
value instead so that `rabbitmqctl delete_vhost` behaves the same
between these changes and the branch fork point.

The `rabbit_vhost_sup_sup:delete_on_all_nodes/1` cleanup is idempotent so
we can run all teardown steps for the vhost and return this error
instead. This might be useful if deletion fails for some resources
under the vhost, for example a queue. If the vhost record is gone it
might still be useful to try to clean up the vhost's resources.

Author: the-mikedavis

deps/rabbit/src/rabbit_vhost.erl

@@ -285,19 +285,19 @@ delete(VHost, ActingUser) ->
     rabbit_log:info("Clearing policies and runtime parameters in vhost '~ts' because it's being deleted", [VHost]),
     _ = rabbit_runtime_parameters:clear_vhost(VHost, ActingUser),
     rabbit_log:debug("Removing vhost '~ts' from the metadata storage because it's being deleted", [VHost]),
-    case rabbit_db_vhost:delete(VHost) of
-        true ->
-            ok = rabbit_event:notify(
-                   vhost_deleted,
-                   [{name, VHost},
-                    {user_who_performed_action, ActingUser}]);
-        false ->
-            ok
-    end,
+    Ret = case rabbit_db_vhost:delete(VHost) of
+             true ->
+                 ok = rabbit_event:notify(
+                        vhost_deleted,
+                        [{name, VHost},
+                         {user_who_performed_action, ActingUser}]);
+             false ->
+                 {error, {no_such_vhost, VHost}}
+         end,
     %% After vhost was deleted from the database, we try to stop vhost
     %% supervisors on all the nodes.
     rabbit_vhost_sup_sup:delete_on_all_nodes(VHost),
-    ok.
+    Ret.
 
 -spec put_vhost(vhost:name(),
     binary(),

deps/rabbitmq_management/src/rabbit_mgmt_wm_vhost.erl

@@ -88,11 +88,7 @@ accept_content(ReqData0, Context = #context{user = #user{username = Username}})
 
 delete_resource(ReqData, Context = #context{user = #user{username = Username}}) ->
     VHost = id(ReqData),
-    try
-        rabbit_vhost:delete(VHost, Username)
-    catch _:{error, {no_such_vhost, _}} ->
-        ok
-    end,
+    _ = rabbit_vhost:delete(VHost, Username),
     {true, ReqData, Context}.
 
 is_authorized(ReqData, Context) ->