LU-8066 obd: make health_check sysfs compliant

LU-8066 obd: make health_check sysfs compliant

The patch http://review.whamcloud.com/16721 was
ported to the upstream client but was rejected
since it violating the sysfs one item rule. Change
the reporting of LBUG plus unhealthy to just
reporting LBUG. Move the reporting of which device
is unhealthy to a new debugfs file that mirrors
the sysfs file.

Change-Id: Ie1640399e97902272000313bb7ccdcbd2be6daf6
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: https://review.whamcloud.com/25631
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Emoly Liu <emoly@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>