Bug#338200: root raid should use mdadm --config=partitions

[dean gaudet <dean@arctic.org>]

Package: initrd-tools
Version: 0.1.84

currently for a root on md raid mkinitrd does something like this:

mdadm -A /dev/md3 -R -u 2b3a5b77:c7b4ab81:a2b8322a:db5c4e88 /dev/sdb4 /dev/sda4

however this has the problem that it will require the root raid devices to 
always reside at /dev/sda4 and /dev/sdb4.  in practice it's way more 
desirable to let mdadm go find the root devices using the UUID -- so that 
if you have to shuffle drives/controllers around the system will still 
boot without problems.  the way to do this is:

mdadm -A /dev/md3 -R --config=partitions -u 2b3a5b77:c7b4ab81:a2b8322a:db5c4e88

note that the devices aren't specified at all -- mdadm will look at any 
and all partitions for raid superblocks with the specified UUID.

i'd suggest using --config=partitions by default and possibly providing a 
mkinitrd.conf option to revert to the explicit device name list.

-dean