MINOR: quic: remove address concatenation to ODCID

MINOR: quic: remove address concatenation to ODCID

Previously, ODCID were concatenated with the client address. This was
done to prevent a collision between two endpoints which used the same
ODCID.

Thanks to the two previous patches, first connection generated CID is
now directly derived from the client ODCID using a hash function which
uses the client source address from the same purpose. Thus, it is now
unneeded to concatenate client address to <odcid> quic-conn member.

This change allows to simplify the quic_cid structure management and
reduce its size which is important as it is embedded several times in
various structures such as quic_conn and quic_rx_packet.

This should be backported up to 2.7.