Provide a minimal implementation of a luks file system class which only
does busy detection.
NOTE:
For now, read-only LUKS support, a LUKS partition will be busy when a
dm-crypt mapping exists. Later when read-write LUKS support is added
GParted will need to look at the busy status of the encrypted file
system within the open LUKS partition and map LUKS partition busy status
to encryption being open or closed.
Bug 760080 - Implement read-only LUKS support
Mike Fleetwood