mdmon: Stop keeping track of RAID0 (and LINEAR) arrays.

mdmon: Stop keeping track of RAID0 (and LINEAR) arrays.

Tracking RAID0 arrays doesn't really work.  There is no need,
and there are some sysfs files which won't exist when the array
appears and then won't be opened when the level is changed.

So simply ignore RAID0 and LINEAR arrays - don't add them when they
appear and if an array we are monitoring turns into one of these,
discard it promptly.

Signed-off-by: NeilBrown <neilb@suse.de>