A Recursor configured to send out ECS enabled queries can be sensitive to spoofing attempts

An attacker spoofing answers to ECS enabled requests sent out by the Recursor has a chance of success higher than non-ECS enabled queries. The updated version include various mitigations against spoofing attempts of ECS enabled queries by chaining ECS enabled requests and enforcing stricter validation of the received answers. The most strict mitigation done when the new setting outgoing.edns_subnet_harden (old style name edns-subnet-harden) is enabled.