[GFS2] Add gfs2_tool lockdump support to gfs2 (bz 228540)

The attached patch resolves bz 228540.  This adds the capability
for gfs2 to dump gfs2 locks through the debugfs file system.
This used to exist in gfs1 as "gfs_tool lockdump" but it's missing from
gfs2 because all the ioctls were stripped out.  Please see the bugzilla
for more history about the fix.  This patch is also attached to the bugzilla
record.

The patch is against Steve Whitehouse's latest nmw git tree kernel
(2.6.21-rc1) and has been tested on system trin-10.

Signed-off-by: Robert Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>