gfs2: Partially revert "gfs2: do_xmote fixes"

When the lm_lock hook which calls dlm_lock() returns an error,
do_xmote() previously reported the error to the syslog ("lm_lock ret
%d\n") but otherwise ignored it during withdraws.  Commit 9947a06d
("gfs2: do_xmote fixes") changed that to pass the error on to the glock
layer, but the error would then only result in an unconditional BUG() in
finish_xmote(), which doesn't help.  Instead, revert to the previous
behavior.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: Andrew Price <anprice@redhat.com>