Share unittest between v2 and v2.1 for hide_server_addresses extension

This patch make the v2.1 hide_server_addresses extension running on v2
unittest, also delete the v3 unittest.

Partially implements blueprint v2-on-v3-api

Change-Id: I9b8e8d10ba59b344d5bdf285fffffd98ed02ebc0
Merge "Share unittest between v2 and v2.1 for hide_server_addresses extension"