ipv6: Fix default multicast hops setting.

As per RFC 3493 the default multicast hops setting
for a socket should be "1" just like ipv4.

Ironically we have a IPV6_DEFAULT_MCASTHOPS macro
it just wasn't being used.
Reported-by: Elliot Hughes <enh@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/af_inet6.c

@@ -200,7 +200,7 @@ lookup_protocol:
 
 	inet_sk(sk)->pinet6 = np = inet6_sk_generic(sk);
 	np->hop_limit	= -1;
-	np->mcast_hops	= -1;
+	np->mcast_hops	= IPV6_DEFAULT_MCASTHOPS;
 	np->mc_loop	= 1;
 	np->pmtudisc	= IPV6_PMTUDISC_WANT;
 	np->ipv6only	= net->ipv6.sysctl.bindv6only;