running in rc.sysinit...leave array starting to it instead
- Modify mdadm to put its mapfile in /dev/md instead of /var/run/mdadm
since at startup /var/run/mdadm is read-only by default and this breaks
incremental assembly
- Change how mdadm decides to assemble incremental devices using their
preferred name or a random name to avoid possible conflicts when
plugging a foreign array into a host
