Fix retaging of ovn-dbs container during update.
Fix retaging of ovn-dbs container during update.

The variable name was wrong, and the retaging was not taking place
leading to ovn dbs being stopped on the cluster after update.

Change-Id: I9f3502be850a48f2aaf018c7cde0fea253a1513a
Closes-Bug: #1839635

openstack/tripleo-heat-templates,openstack/tripleo-heat-templates