Always enable boot.lvm on Cinder-volume nodes

For LVM backend, we need lvm auto-activation to be running on
boot, otherwise cinder volumes are dead after a reboot of the
node. This is disabled on SLES by default, so we need to
activate the appropriate boot script.
Style nitpick: use 'include? X' instead of 'include?(X)'
Merge pull request #110 from dirkmueller/pebbles_activate_boot_lvm

Always enable boot.lvm on Cinder-volume nodes