add local non-SSL listener for web UI

The cli tool `rabbitmqadmin`, which is used by the `rabbitmq_vhost` provider, by default connects to port 15672. Commit 7f5a21f changed the previous behaviour from always listening on port 15672 to not listening on port 15672 when ssl was set, breaking `rabbitmqadmin` and the `rabbitmq_vhost` provider as it had no way of knowing which port or whether it needed to connect to the web UI over SSL or not.

Here's an error from commit 7f5a21f:
```
Error: Execution of '/usr/local/bin/rabbitmqadmin declare exchange --vhost=/my_vhost --user=my_user --password=my_pass name=my_exchange type=topic' returned 1: *** Could not connect: [Errno 101] Network is unreachable
```
Having it listening on localhost:15672 was the simplest solution.