Make python-guestfs NOPRIME & install for libvirt

The libguestfs dependency tree includes a number
of packages that we may not want or work everywhere, such as fuse.

Now python-(lib)guestfs will install from lib/nova_plugins/hypervisor-libvirt

Change-Id: I6c3a614010ee8d65813eec66a56680def622514c
Merge "Make python-guestfs NOPRIME & install for libvirt"