(currently only CD-ROM drives on i386). The sys/dev/scsipi system provides 2
busses to which devices can attach (scsibus and atapibus). This needed to
change some include files and structure names in the low level scsi drivers.
that a unit select did not complete and needs to be retried. Selection will
be retried following a disconnection if this flag is set. The function
sfas_select_unit() will set/clear this flag depending on when a selection
completed or not.
