Support remote VM hosts in boot-seed-vm.
Support remote VM hosts in boot-seed-vm.

With the upcoming test cluster, we need the ability to boot seed VMs
that are stored on a remote machine. This involves copying the image
onto the machine, chattr +C'ing it and then calling virsh start with
an appropriate URI.

Change-Id: I6194ad94d96aec08105f11acfae61b674a6f15c0

rdo-management/tripleo,rdo-management/tripleo