dht/ice: swap IPv4 vs IPv6 dht address priority

Use IPv4 over IPv6 if both available from DHT.
IPv6 are less NAT'ed so using host addresses is enought to establish
connection over IPv6.
But it's not the case for IPv4 and must be given in priority if available
over IPv6 addresses.

Change-Id: Ia7243f415ebaf81208e175b6f5e704263b7594fd