gfs2: Switch lock order of inode and iopen glock

This patch tries to fix the continual ABBA deadlocks we keep having
between the iopen and inode glocks. This switches the lock order in
gfs2_inode_lookup and gfs2_create_inode so the iopen glock is always
locked first.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>