Fix broken rabbitmqctl commands when using ipv6

Fix broken rabbitmqctl commands when using ipv6

When deploying via ipv6, rabbitmq-ctl commands have the following
issues:

- `rabbitmq cluster_status` shows nodedown alerts
- list_queues / list_connections hang
- `rabbitmqctl node_health_check` fails with an error.

* There is no any issue while performing activity on RHOS setup(From
* horizon/cli). i.e. RHOS environment is functioning as expected.

For example:
sudo rabbitmqctl node_health_check -n rabbit@node1
Checking health of node 'rabbit@node1' ...
Heath check failed:
health check of node 'rabbit@node1' fails: nodedown

The problem is that we are missing the following in
/etc/rabbitmq/rabbitmq-env.conf:
RABBITMQ_CTL_ERL_ARGS="-proto_dist inet6_tcp"

Fix these by setting the appropriate RABBITMQ_CTL_ERL_ARGS when
deploying ipv6.

Closes-Bug: #1633693
Change-Id: I53f4e76e687b3966fbb74fd0c2d83f05176630de