1) peers update their neighbourood when:
a - they receive an explicit "add/remove peer to neighbours" message;
b - when they see it's time to (when UPDATE_PEERS_TIMEOUT expires);
2) when a gossiping message is received, newscast cache is updated, but NO
modification to current neighbourood happens.
3) black list insertion is now driven by get_transmitter lossrate function.
Signed-off-by: Stefano Traverso <firstname.lastname@example.org>