Changes V3 evacuate extension into v2.1

This patch changes v3 evacuate API to v2.1, and also share v2.1 and v2
test case.
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: Ib105e367be5a921f1b9cade51204b224d99343ec
Merge "Changes V3 evacuate extension into v2.1"