Retry writing 'inactive' state during stopping array

Retry writing 'inactive' state during stopping array

Issue observed:
Sporadicaly stopping arrays using "mdadm -Ss" command does not succeded.
Cause:
Writting "inactive" to the array state not succeded- array is busy
(accessed by udev, blkid etc.)
Resolution:
If writing 'inactive' fails, wait and retry again (because it is possibly
a transient failure)

Signed-off-by: Krzysztof Wojcik <krzysztof.wojcik@intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>