ZED will diagnose a fault on a disk that has exceeded the threshold.
It looks like it doesn't correctly handle the situation where one of
a raidz children is undergoing a resilver and the faulted disks exceed
the redundancy guarantees.
This patch will prevent ZED from issuing any vdev faults and instead
will degrade the vdev.
Signed-off-by: Don Brady <don.brady@klarasystems.com>