Prevent force delete if the volume is attached

Force deletes were eventually failing on the volume manager layer due to
being in an attached state. This will check that up front to inform the
user that they need to detach first.

Fixes: bug #1164929
Change-Id: I24ade24fd750dc647331ef25b835f45f29c10fd7
Updating HACKING to disallow the use of locals()

Change-Id: I7bf2720bdb0456274dc81a73d91296dff0e3fced
Merge "Updating HACKING to disallow the use of locals()"
Merge "Prevent force delete if the volume is attached"