scsi_debug: add Report supported opcodes+tmfs; Compare and write

The Report supported operation codes command is very closely integrated
into the table driven parser and very useful for testing it. Its cdb
masks form the basis of the 'strict' parameter's checks. The Report
supported TMFs command is a simple extension. The Compare and write
command may even be useful, as it should be atomic due to the read-write
lock that the driver uses on its backing store (ram).
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>