Bug#774762: try harder to find reasons for failed `lvchange -an` by looking at /proc/*/mountinfo

[Peter Rajnoha]

I'd say the best "who-uses" tool in this case is "lsblk" - it's directly
a part of util-linux which is everywhere and it shows quickly the block
device tree as well as mount status (it just looks at sysfs info and
provides it in nice human readable form, machine readable form is also
possible though for use in scripts). LVM itself already uses this tool
within helper "blkdeactivate" script that deactivates tree of DM/LVM
devices.