[jdk17u] RFR: 8269481: SctpMultiChannel never releases own file descriptor

[Alex Kasko]

Clean backport of the SCTP fix.

Additional testing:

 - [x] with SCTP enabled in OS checked that added test fails without the patch and passes with the patch
 - [x] ran jtreg:jdk/com/sun/nio/sctp/

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Commit messages:
 - Backport d1cecaaa22d551b93074c33209dac7354f4b6932

Changes: https://git.openjdk.java.net/jdk17u/pull/247/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk17u&pr=247&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8269481
  Stats: 145 lines in 4 files changed: 142 ins; 3 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk17u/pull/247.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17u pull/247/head:pull/247

PR: https://git.openjdk.java.net/jdk17u/pull/247