ssc: MODE SELECT test Save Page bit before processing mode pages

Return CHECK CONDITION / INVALID FIELD IN CDB if SP bit set

T10.org doco is a little vague on what to do if SP is not supported and
if MODE PAGE data should/should not be processed.

Sebasitan identified HP LTO5 documentation which clarified HP
behaviour. Modeling mhVTL behaviour on HP.

Reported-by: Sebastian Herbszt <herbszt@gmx.de>
Signed-off-by: Mark Harvey <markh794@gmail.com>