ocfs2: Remove ->hangup() from stack glue operations.

The ->hangup() call was only used to execute ocfs2_hb_ctl.  Now that
the generic stack glue code handles this, the underlying stack drivers
don't need to know about it.

Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>