[PATCH] Use device ids instead of paths for action pruning. (#500808)

[David Lehman <dlehman redhat com>]

The second patch modifies action queue pruning to use device ids instead of
paths. This, in conjunction with the patch to update PartitionDevices' names
to correspond with parted's renumbering after a removal, frees us from the
issue of losing track of devices because of parted's renumbering of
partitions.

It also provides us with a mechanism to better track protected partitions.
All we have to do is note the id of the protected partition(s) after
populating the device tree.