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: I72b52968433019dc7dff4f7a92ad1ac65dee554a
Tracked-On: https://jira01.devtools.intel.com/browse/AW-7202


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>
Signed-off-by: Wajdix Zairi <wajdix.zairi@intel.com>
Reviewed-on: https://android.intel.com/600492


Reviewed-by: Dubray, SimonX <simonx.dubray@intel.com>
Reviewed-by: Tasayco Loarte, VictorX <victorx.tasayco.loarte@intel.com>
Reviewed-by: Ledentec, AlexandreX <alexandrex.ledentec@intel.com>