MINOR: remove the client/server side distinction in SI addresses

Stream interfaces used to distinguish between client and server addresses
because they were previously of different types (sockaddr_storage for the
client, sockaddr_in for the server). This is not the case anymore, and this
distinction is confusing at best and has caused a number of regressions to
be introduced in the process of converting everything to full-ipv6. We can
now remove this and have a much cleaner code.
diff --git a/src/stream_sock.c b/src/stream_sock.c
index d673aba..d6fd54e 100644
--- a/src/stream_sock.c
+++ b/src/stream_sock.c
@@ -517,7 +517,7 @@
 		 * it is positive, it means we have to send from the start.
 		 */
 		ret = make_proxy_line(trash, sizeof(trash),
-				      &b->prod->addr.c.from, &b->prod->addr.c.to);
+				      &b->prod->addr.from, &b->prod->addr.to);
 		if (!ret)
 			return -1;