Comment 3 for bug 1925436

According to gnuoy's comment for patchset 3 in the page [1], I've refactored the code and implemented his idea. so now we have two patches:

1, heat side, see [2]
2, rabbitmq-server side, still see [1]

[1] https://review.opendev.org/c/openstack/charm-rabbitmq-server/+/787909
[2] https://review.opendev.org/c/openstack/charm-heat/+/792795