Add the md_activate function
Fix missing colon in the annotation
Use smaller temp files for MD RAID testing

Since contents of these files are synced when the RAID is started, they quickly
grow big.
Use the /dev/md/ prefix when deactivating MD RAID

The mdadm doesn't understand user-defined names of MD RAID devices on their own,
they need to be specified with a full path (with the /dev/md/ prefix).
Let udev settle after creating MD RAID

This way the /dev/md/ user-defined device node symlinks are surely created
before we start using them.

Also use a better user-defined name for our testing RAID.
Use "--find_multipaths y" for mpath set_friendly_names

--find_multipaths is important to keep multipath from making up multipath
devices that aren't really multipath