Make boot.looplvm a SUSE-only service

The init script doesn't really work on other distros atm
Re-run boot.lvm on loopback mount

Otherwise LVM hasn't really discovered the newly added VG
Fix description of rbd_user parameter

This is more understandable.
Merge pull request #136 from dirkmueller/rados_naming

Fix description of rbd_user parameter
Merge pull request #135 from dirkmueller/release/roxy/master

Rediscover VGs after boot in file backend case
Fix crash with boot.looplvm service not being defined

It cannot be defined in an optional path and referenced in the
notification of a non-optional resource.
Merge pull request #137 from vuntz/fix-crash

Fix crash with boot.looplvm service not being defined