gfs2: Fix GLF_INVALIDATE_IN_PROGRESS flag clearing in do_xmote

Commit 865cc3e9 ("gfs2: fix a deadlock on withdraw-during-mount")
added a statement to do_xmote() to clear the GLF_INVALIDATE_IN_PROGRESS
flag a second time after it has already been cleared.  Fix that.

Fixes: 865cc3e9 ("gfs2: fix a deadlock on withdraw-during-mount")
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: Andrew Price <anprice@redhat.com>