IMSM: do not rebuild the array if a non-redundant sub-array with failed disks is...

IMSM: do not rebuild the array if a non-redundant sub-array with failed disks is present

Before looking for a spare to rebuild a degraded array, check if there
are any failed disks in container.  Block rebuild if another sub-array
is failed until failed disks are removed from container.

Currently, Intel metadata handler rebuilds all sub-arrays even if one
of them is non-redundant. In case of failed sub-array, failed disks
are just replaced with new ones in the metadata mapping. The data for
failed disk is not restored even the disk is present in the system.

With this fix, we require the removal of the failed disk from
container to start the process of rebuilding the array with failed
member. If the disk is physically pulled out of the system, the disk
is removed from container automatically by exiting udev rules.

Signed-off-by: Marcin Labun <marcin.labun@intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>