failed rf_ConfigureLayout with 22

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

I just tried to update another server from 8.2 to 10, and it paniced during 
boot with
	RAIDFRAME: failed rf_ConfigureLayout with 22
The line just before that reads:
	WARNING: findroot: double match for boot device (bootinfo/bootwedge:wd0 bootinfo/bootwedge:wd1)
But with the working 8.2 it's similar:
	WARNING: findroot: double match for boot device (wd0, wd1)
and the next lines are:
	raid0: RAID Level 1
	raid0: Components: /dev/dk0 /dev/dk2 /dev/dk4
	raid0: Total Sectors: 134217600 (65535 MB)

All raid0's components are -A softroot.

I switched back to 8.2 and that works again.