appliance: fix newer debian iso links and checksums for debian

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>
(cherry picked from commit ac5309b8b47ddb1e5588a2d5090f2bcce0e7c2a4)
Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>