Do not restart libvirt if n-cpu is disabled

If this service is disable in localrc, libvirt does not installed at all,
and should not be restarted.

Change-Id: Iaf482d4a82a26546c25249b3e32c7e629d862a1b
Closes: bug 1288236
Make mongo install for ceilometer NOPRIME

mongodb packages are missing on some platforms, so we switch to a
manual install.  Also gate the mongo call in cleanup

Change-Id: I1755e461c66be30da3db2a0994f908503c4c38ea
Merge "Make mongo install for ceilometer NOPRIME"
Merge "Do not restart libvirt if n-cpu is disabled"
Merge branch 'master' of https://github.com/openstack-dev/devstack