gfs2: Minor do_xmote cancelation fix

Commit 6cb3b1c2 changed how finish_xmote() clears the GLF_LOCK flag,
but it failed to adjust the equivalent code in do_xmote().  Fix that.

Fixes: 6cb3b1c2 ("gfs2: Fix additional unlikely request cancelation race")
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>