One use case is to use seperate disk for the registry storage. This
can prevent the rootfs from filling up.

Change-Id: I9634ee7f5730e93b8ddd96de04982d638dd4dae2

Change-Id: Ida7b870e86894bd33e923ae1cc1142d32e052ddc
Story: 2004817
Task: 28982

By default the registry listens on port 4000 to avoid clashing with keystone.
It is configured via the following commands:

kayobe overcloud service <deploy|pull|reconfigure|upgrade>