scsi_debug: change SCSI command parser to table driven

The existing 'big switch' parser in queuecommand() is changed to
a table driven parser. The old and new queuecommand() were moved
in the source so diff would not shuffle them. Apart from the new
tables most other changes are refactoring existing response code
to be more easily called out of the table parser. The 'strict'
parameter is added so that cdb_s can be checked for non-zero
values in parts of the cdb that are reserved. Some other changes
include: tweak request sense response when D_SENSE differs; support
NDOB in Write Same(16); and fix crash in Get LBA Status when LBP
was inactive.
Signed-off-by: NDouglas Gilbert <dgilbert@interlog.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>