[AMQP 1.0] amqp1 devstack plugin should set the transport url using env variables

[Ken Giusti]

The amqp1 devstack plugin's get_transport_url() method uses a mix of configuration vars and passed arguments to construct the URL. This is due to the way the plugin hardcodes the default port values.

Instead the transport url should be constructed using just configuration vars. This would require creating a few configuration vars to help with the dual backend deployment:

AMQP1_PORT=5672
AMQP1_NOTIFY_PORT=5671

AMQP1_NOTIFY_HOST=.... - default to AMQP1_HOST if not set

Also get_transport_url should check whether the AMQP1_USERNAME and AMQP1_PASSWORD vars have been set as to avoid introducing ":@host" into the URL if they are not set.

https://review.openstack.org/#/c/404854/