This patch adds support for Octavia API endpoint versioning.
Previously Rocky API additions were being tested, regardless of the Octavia
API version.
It also fixes a potential race condition when testing the "ONLINE"
operating status.
The patch also makes sure that duplicate fixed IP addresses are not allocated
on subnets.
Story: 2003466
Task: 24726
Change-Id: If0ec777f34326c09c7215d9c7c2ed249571d779e