Port extended-availability-zone API into v3 part2

This patch contains the changes required to adapt the
extended-availability-zone extension and the corresponding
unittest to the v3 framework.

Partially implements bp v3-api-extension-versioning

Change-Id: Ifa9b8a0ddb1c5a297d6fcddbaea476192f339784
Merge "Port extended-availability-zone API into v3 part2"