[GFS2] set plock owner in GETLK info

Set the owner field in the plock info sent to userspace for GETLK.
Without this, gfs_controld won't correctly see when the GETLK from a
process matches one of the process's existing locks.

Signed-off-by: David Teigland <teigland@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>