rabbitmq-server slave charm executes too much

[Gema Gomez]

when in HA, rabbitmq-server slave charm executes ['/usr/sbin/rabbitmqctl', 'list_vhosts']

solution: in HA, slave node is not running rabbitmq; do not even try communicating with rabbit. Problem identified in line

in update_nrpe_checks()
    rabbit.create_vhost(vhost) -> shouldn't be happening on slave mode

How to reproduce:

1) Deploy ha openstack by running:

> juju-deployer --bootstrap -c default.yaml precise-havana
 -> from this branch:
lp:~openstack-charmers/+junk/openstack-charm-testing-ha