ocfs2_dlmfs: User DLM_* when decoding file open flags.

In commit 0016eedc

, we have
changed dlmfs to use stackglue. So when use DLM* when we
decode dlm flags from open level.

Signed-off-by: Tao Ma <tao.ma@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>