[GFS2] Fix bug in clear_inode

We should have been waiting for lock demotion to finish in
clear_inode.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 91ac9c9..b6edf7c 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -771,6 +771,7 @@
 	list_add_tail(&gh.gh_list, &gl->gl_waiters2);
 	run_queue(gl);
 	spin_unlock(&gl->gl_spin);
+	wait_for_completion(&gh.gh_wait);
 	gfs2_holder_uninit(&gh);
 }