this script, without it sparc64 ISO building was consistently failing
because the /dev/md0 device name was not present when the commands
following mdconfig ran. Apparently there is the possibility of a delay
between when mdconfig finishes and the names become visible in /dev.
Yes, we could code this better than an unconditional call to "sleep 5"
but IMHO we should fix the underlying problem instead.
MFC after: 3 days
55f7c69395