Adding Nova Client support for auto find host APIv3

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

Change-Id: I40619b8d1eea6ae44ed5e43fb50ce2c1862686d6
Co-Authored-By: Juan M. Olle <juan.m.olle@intel.com>
Merge "Adding Nova Client support for auto find host APIv3"