Remove unnecessary code from idmapd.

This patch removes unnecessary code from idmapd. setproctitle is not used
anywhere and it can be removed. In addition the kernel section of the
nfs_idmap.h header is not used and is out of date and thus is removed.

Signed-off-by: David P. Quigley <dpquigl@tycho.nsa.gov>
Signed-off-by: Kevin Coffman <kwc@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>