We should be shutting down rpciod for the callback channel when we shut down
the server.

Also note that we do rpciod_up() and create the callback client *before*
setting cb_set--the cb_set only determines whether the initial null was
succesful.  So cb_set is not a reliable determiner of whether we need to clean
up, only cb_client is.
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>