Fix rabbitmq_policy to work with 3.1.5.  Fixed #16024

Fixed code to detect and interpret both 5 and 6 field outputs from
rabbitmqctl.  Also prevented no priority from triggering an update
on every state run (due to comparing int with str).
Merge pull request #16025 from loz-hurst/develop

Fix rabbitmq_policy to work with 3.1.5.  Fixed #16024