do not use --allow-downgrades on Jessie, refs #679 #666 (#686)
do not use --allow-downgrades on Jessie, refs #679 #666 (#686)

Signed-off-by: Holger Friedrich <1d6e1cf70ec6f9ab28d3ea4b27a49a77654d370e@holger-friedrich.de>
openhab/openhabian,ThomDietrich/openhabian,openhab/openhabian,openhab/openhabian