As described in blockdevice.py detachment and (most) resources
release must be done in the umount phase of a block device module.
Until now these jobs were done in the lvm cleanup() phase - which
is too late - especially when using nested LVMs.
This patch moves the functionality of the cleanup() phase to the
umount() phase for the lvm module.
It includes a test case that fails without applying the provided
source code changes.
Change-Id: I697bfbf042816c5ddf170bde9534cc4f0c7279ff
Signed-off-by: Andreas Florath <andreas@florath.net>
f5736f3178