cache: scrubbing for cache origin LV - Bug 1169495

cache: scrubbing for cache origin LV - Bug 1169495

Allow RAID scrubbing on cache origin sub-LV

This patch adds the ability to perform RAID scrubbing on the cache
origin sub-LV (https://bugzilla.redhat.com/1169495).  Cache origin
operations are restricted to non-clustered RAID LVs until there can
be further testing in a cluster (even for exclusive activation).

User can either specify directly _corig LV
or he can specify cache LV and operation  --syncation is
passed ONLY to   _corig LV.

If users wants to manipulation with cache-pool devices - he
needs to specify this object name.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>