Ensure that API does not allow conflicting policies to be configured
on an instance group. More specifically the user should not be allowed
to configured 'anti-affinity' and 'affinity' on the same instance group.
In addition to this a validation will also be done on the policy, that is,
if the policy is not supported then an exception will be raised.
This is part of blueprint instance-group-api-extension.
Change-Id: Id19c55cb60109819429f73e2b28efe7f15cc5194
Support the Creation, Read, Delete, and List of server groups.
Refactored the code to use objects (https://review.openstack.org/#/c/38979/
Renamed from "instance group" to "server group".
Implements: blueprint instance-group-api-extension
Change-Id: I650a8f191dea5eab5b4b1828f0b9f65e33edea2a
Gary Kotton