ocfs2: o2hb: don't negotiate if last hb fail

ocfs2: o2hb: don't negotiate if last hb fail

Sometimes io error is returned when storage is down for a while.
Like for iscsi device, stroage is made offline when session timeout,
and this will make all io return -EIO. For this case, nodes shouldn't
do negotiate timeout but should fence self. So let nodes fence self
when o2hb_do_disk_heartbeat return an error, this is the same behavior
with o2hb without negotiate timer.

Oracle-bug: 21862940

Signed-off-by: Junxiao Bi <junxiao.bi@oracle.com>
Reviewed-by: Ryan Ding <ryan.ding@oracle.com>