When host sends TEST UNIT READY command, set sense 'all ok' if block device reports
that medium is inserted, or set sense 'medium not present' if medium is not inserted.
Do not override sense by default with 'all ok', allow REQUEST SENSE command
to be responded with correct sense data which was set on last failure.
Check just DESC bit when responding to REQUEST SENSE command.
Romain Reignier
Kimmo Lindholm
barthess