Bug#225648: apt: seperate config variable for disabling CheckAuth
CheckAuth checks if APT::Get::Assume-Yes is true to bypass the check.
This is problematic for build daemons, where you don't want to allow
package statuses to be changed unless requested by the buildd (what
APT::Get::Assume-Yes only did before the secure patch), but you do
want to allow unauthenticated packages. A seperate config variable should
be used for this. APT::Get::AllowUnauthenticated or so?