sctp: backports from upstream, 2nd phase

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2160516 Tested: lksctp-tools func_tests

v1-v2:

• add the whole patchset of "inet6: Remove inet6_destroy_sock() calls" instead of only 2 patches of them, as Davide suggested. v2->v3
• drop patch "sctp: delete free member from struct sctp_sched_ops" which is a code improvement, as it may cause stuck. v3->v4:
• drop patch "sctp: fix memory leak in sctp_stream_outq_migrate()" which cause another stuck.

Signed-off-by: Xin Long lxin@redhat.com