LU-1346 contrib: fix libcfs_cleanup script

LU-1346 contrib: fix libcfs_cleanup script

Fix up some warnings in the contrib/scripts/libcfs_cleanup.sed script.
Add a comment with details on how to run the script to find missing
conversions.

Exclude the gnilnd subdirectory, as James prefers to update this
himself.

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: If61c4318e9d4e7bb59592dfef5c9ee4f973ebbe5
Reviewed-on: http://review.whamcloud.com/6824
Reviewed-by: Christopher J. Morrone <chris.morrone.llnl@gmail.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Tested-by: Hudson
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>