Add zedlet to ZFS ZED that markes OFD as degraded/undegraded,
when a zpool is degraded or online, respectivly.

Test-Parameters: trivial
Signed-off-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Change-Id: Ia8ec3cf3a31ce24d8598d690bcb0356245712858
Reviewed-on: https://review.whamcloud.com/30907


Tested-by: Jenkins
Reviewed-by: Olaf Faaland-LLNL <faaland1@llnl.gov>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>