The policies field has been replaced with the
policy field since Nova API version 2.64[1]
This commit adds a check to make sure the correct field is used.
[1]https://docs.openstack.org/nova/latest/reference/api-microversion-history.html#id59
Change-Id: I06d3211937d822c26070b7f8ad757c365dcbb1bb
Story: #2007822
Task: #40101
(cherry picked from commit 51a1ea65f4)