Remove bucoord/expire.c

It was not compiled into anything.

Correct references in bucoord_internal to command.c.

Remove the forward declaration of struct cmd_parmdesc and make cmd.h
a prerequisite for this header, since all but two consumers had cmd.h
already.

Change-Id: Id60a550871643610ccd96c226ecf0a3c4acb3955
Reviewed-on: http://gerrit.openafs.org/10363
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>