This diff fixes a following bug:
When the queue for the tunnelbroker-id is not created (clean rabbitMQ instance) there is an error when creating a new one:
```
AMQP: Queue creation error: PRECONDITION_FAILED - inequivalent arg 'x-expires' for queue 'tunnelbroker1' in vhost '/'.
```
We must remove converstion to the `string` when initializing the queue attribute. That fixes the error.