Add tests for cassandra/retry_policy.py
Add tests for cassandra/retry_policy.py

Story: 2007280
Task: 38724

Depends-On: https://review.opendev.org/#/c/679076/

Change-Id: I440e36ad37dc94ffcd665f3925b7f25b5964cbf8

openstack/monasca-persister,openstack/monasca-persister,openstack/monasca-persister