[jdk15u-dev] Integrated: 8274736: Concurrent read/close of SSLSockets causes SSLSessions to be invalidated unnecessarily

[Yuri Nesterenko]

clean backport; new and old tests do pass.

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Commit messages:
 - Backport 8822d41fdcc2c2d568badd72635dc587d21dbd63

Changes: https://git.openjdk.java.net/jdk15u-dev/pull/172/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk15u-dev&pr=172&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8274736
  Stats: 429 lines in 3 files changed: 425 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk15u-dev/pull/172.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk15u-dev pull/172/head:pull/172

PR: https://git.openjdk.java.net/jdk15u-dev/pull/172