This avoids us leaving the filter in the global lvm config. Without cleaning
this up, we can hit some failures to run stack.sh because devices are excluded
that we need to be able to see. This resets it to what it was before when
we do a cleanup.
Also, do this before we add the line, so we don't add multiple lines on
successive runs.
Closes-bug: #1437998
Change-Id: Idbf8a06b723f79ef16a7c175ee77a8c25f813244
6cdb2e0f1a