Find devices by partition GUID and exclude mounted devices

Facter function now uses partition GUID instead of filesystem label
to find matching devices. It also excludes already mounted devices.
This depends on https://review.openstack.org/#/c/54841/.
See also https://bugs.launchpad.net/fuel/+bug/1246513
Merge pull request #773 from xarses/ceph-disk-unformatted

Update Ceph OSD device list generation