Add live migration support and firewall rules

The nova live migration url was set to qemu_ssh//... which doesn't work
on Red Hat distributions as the user in the packages is set up with a
nologin shell.
The desired way to do live migrations is to use qemu+tcp://...
The libvirt config option (listen_tcp) is already set to 1 in this
patch - https://review.openstack.org/#/c/106436/

Fixes: rhbz#1122457, rhbz#1122703, rhbz#1117524

Change-Id: I36055847fa293edb63a972a0c9f597bc2e27b7ab