Fix get_force_authn return value to be compatible with older pysaml2
Fix get_force_authn return value to be compatible with older pysaml2

older pysaml2 cannot parse False as a value for force_authn

Signed-off-by: Ivan Kanakarakis <f60d6943d72436645c4304926eeeac2718a1142c@gmail.com>

SUNET/SATOSA,its-dirg/SATOSA,SUNET/SATOSA