Refactor nova migration config into client & target profiles

Refactor nova migration config into client & target profiles

The nova migration config has always been applied by the base::nova profile.
It assumed that libvirtd/nova-compute and are all running on the
same host.
Where this config didn't apply (e.g a nova api host) it was disabled by a flag.

This approach is not compatible with containers. Hieradata for all containers
are combined so per-host flags no longer work, and we can no longer assume
libvirtd and nova-compute run in the same context.

This change refactors the profiles out of the base nova profile and into
a client profile and a target profile that can be included where appropriate.

Change-Id: I063a84a8e6da64ae3b09125cfa42e48df69adc12
Implements: blueprint tripleo-cold-migration