Bugfix for candidate transport matching in conncheck

The first patch ensures that we select the local candidate having a compatible matching transport with the remote candidate. In rare cases, when having a reduced port range for example, we may have tcp and udp local candidates having the same address and port number.

The second patch modifies the function priv_match_remote_candidate_transport_and_socket_type that helps to find the correct remote candidate based in the nice socket, and its remote address and port number. When several remote candidates are possible, with the same address and port, we match the reliability of the (base) socket that received the packet.