Change V3 access_ips extension into v2.1

This patch changes v3 access_ips API to v2.1 and makes v2
unit tests share between v2 and v2.1.
The differences between v2 and v3 are described on the wiki page
https://wiki.openstack.org/wiki/NovaAPIv2tov3 .

Partially implements blueprint v2-on-v3-api

Change-Id: Id464cbe4a8b7a7749c4f14e4531e4494dd315857
Merge "Change V3 access_ips extension into v2.1"