Convert migrate_server v3 plugin to v2.1

Changes required to have v3 plugin natively support
the v2 API.

The migrate_live action is reverted back to os-migrateLive

Partially implements blueprint v2-on-v3-api

Change-Id: Ib3332ecfbf47ed6cad6108399083f0c26b7eebfe
Merge "Convert migrate_server v3 plugin to v2.1"