Port evacuate API to v3 Part 1

This changeset only copies the v2 files (implementation and test)
into the appropriate v3 directories unchanged. The copy as-is
will not be loaded by either the v2 or v3 extension loaders. The
second changeset will then make the changes required for it to
work as a v3 extension.

This is being done in order to make reviewing of extension porting
easier as gerrit will display only what is actually changed for v3
rather than entirely new files

Partially implements blueprint nova-v3-api

Change-Id: I2c77b445b1e7a1b63993ae86cebea9922e9d098c
Port evacuate API to v3 Part 2

This patch contains the changes required to adapt the evacuate
extension and the corresponding unittest to the v3 framework

Partially implements blueprint nova-v3-api

Change-Id: Id9ca6a7a92a087cb063fe265af1ad6a626c63510
Merge "Port evacuate API to v3 Part 1"
Merge "Port evacuate API to v3 Part 2"