ipv6/dccp: do not inherit ipv6_mc_list from parent

Like commit 657831ffc38e ("dccp/tcp: do not inherit mc_list from parent")
we should clear ipv6_mc_list etc. for IPv6 sockets too

Change-Id: I600f5029ea88fc52e33ec3f5775a52c3efdd07cf
Git-commit: 83eaddab4378db256d00d295bda6ca997cd13a52
Git-repo: https://source.codeaurora.org/quic/la/kernel/msm-3.10


Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[srkupp@codeaurora.org: Resolved minor conflict]
Signed-off-by: Srinivasa Rao Kuppala <srkupp@codeaurora.org>