Pull up following revision(s) (requested by jdc in ticket #1251):
sys/arch/sparc/stand/bootblk/bootblk.fth: revision 1.8
Instead of bailing out with "Inode not directory", assume that the disk is
a RAIDframe mirror, apply the RAID boot offset, and try to boot again.
Fixes the problem where disks would be unbootable if partitioned normally
and then converted to RAID 1 without being zeroed first.

(bouyer)