There are two methods for setting up RabbitMQ HA:
1. Configure rabbit_hosts to multi rabbit hosts.
2. Setting up a loadbalancer in front of RabbitMQ cluster,
provide a unique address in rabbit_host
In current, rabbit_ha_queues option is controled by rabbit_hosts IF
conditional statement. But when users want to use the second method:
changing rabbit_ha_queues to true, but they don't use rabbit_hosts
option, this logic will not work.
This patch adds an rabbit_ha_queues option, set it to undef by
default for forward compatbility.
Close-Bug: #1485287
Change-Id: Ib8fe16182188729100ef4704466c4d42d31ff510
2443294da2