[SCSI] Fix DVD burning issues.

Some pioneer DVDs are apparently returning odd "not ready" status
codes that the mid-layer doesn't recognise and so passes back to the
user as errors.

This patch overhauls our not-ready handling and adds transparent retries for:

format in progress
rebuild in progress
recalculation in progress
operation in progress
Long write in progress
self test in progress

The Pioneer was actually returning "long write in progress"

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>