This patch removes the unneeded dd calls in the lvm block device
plugin.
After removing the underlying block device, there is the need to call
'pvscan --cache'. This is done by a dedicated LVM cleanup node which
is cleaned up after the the underlying block device.
Change-Id: Id8eaede77fbdc107d2ba1035cd6b8eb5c10160c3
Signed-off-by: Andreas Florath <andreas@florath.net>