[jdk11u-dev] RFR: 8213235: java/nio/channels/SocketChannel/AsyncCloseChannel.java fails with threads that didn't exit

[Aleksey Shipilev]

Backporting to match `11.0.13-oracle`. This backport contains two fixes that are done in lock-step with each other.

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Commit messages:
 - Backport a6f0e10fe8fdfe933684e0304f4918e54cb104e7
 - Backport 836e02e1f1ef696c73269123e5ec2b71f56fb5ce

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/218/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=218&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8213235
  Stats: 10 lines in 1 file changed: 3 ins; 1 del; 6 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/218.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/218/head:pull/218

PR: https://git.openjdk.java.net/jdk11u-dev/pull/218