Deploy cloud hypervisor type

Proposes a method for varying the hypervisor type used by Nova in the
deploy cloud to deploy overcloud services from baremetal/ironic to any
other hypervisor type supported by Nova. In particular, containers and
Docker make this deployment attractive due to their lightweight nature.

Change-Id: I7d153b0341e148274590d3d049cf0e2141369e58
Merge "Deploy cloud hypervisor type"