nova: manage migration bits in a composable way
nova: manage migration bits in a composable way

Allow to enable/disable migration bits from a single place, and select
which services are running on a node.
The use case here is to allow container deployements where libvirt &
nova-compute are separated.
Also support collocation for backward compatibility.

Change-Id: I0b765f8cb08633005c1fc5a5a2a8e5658ff44302

openstack/puppet-tripleo,openstack/puppet-tripleo,openstack/puppet-tripleo