RFR: 8269481: SctpMultiChannel never releases own file descriptor [v4]

[Brian Burkhalter]

> Please review this change to the Unix implementations of `sun.nio.ch.sctp.Sctp*ChannelImpl#kill()` to close the socket if `state == ChannelState.UNINITIALIZED`.

Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision:

  8269481: Fix incorrect order of setting state to KILLED and closing the socket

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4621/files
  - new: https://git.openjdk.java.net/jdk/pull/4621/files/c8865603..676c0f0a

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4621&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4621&range=02-03

  Stats: 6 lines in 3 files changed: 3 ins; 3 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4621.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4621/head:pull/4621

PR: https://git.openjdk.java.net/jdk/pull/4621