Filter out Cinder VG from LVM

Without filtering out the cinder-volumes VG, LVM will happily
scan and import VGs defined on any block devices within /dev.

This commit adds a filter rule in /etc/lvm/lvm.conf which rejects
devices which match node['cinder']['storage']['lvm']['volume_group'].

Fixes DE253
Merge pull request #73 from DavidWittman/lvm-filter

Merged automatically by jenkins after successful build test