Adding Nova Client support for auto find host APIv2

Adding nova client functionality to use the auto find
destination host for evacuate.
This change makes the target host optional
on evacuate command.

Partial Implements: blueprint find-host-and-evacuate-instance

Co-Authored-By: Leandro Costantino <leandro.i.costantino@intel.com>
Change-Id: I4e6b52df9c55b223c8693058d73125962cff4d16
Merge "Adding Nova Client support for auto find host APIv2"