Merge branch 'sctp-race-fix'

Xin Long says:

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sctp: fix the race condition in sctp_destroy_sock in a proper way

The original fix introduced a dead lock, and has to be removed in
Patch 1/2, and we will get a proper way to fix it in Patch 2/2.
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Signed-off-by: David S. Miller <davem@davemloft.net>