In Agent::isUs() check for comparison of maddr parameter AND host field. This is useful for cases where the flexisip is behind a NAT and configured with a canonical name in transports definition, so that isUs() can recognize a Route that points to the proxy.
Additionally, this commit reworks a bit the Agent's code by caching the use-maddr config parameter (optimization) and reduces the size of Agent::start() by making a specific method for mDNS handling.