[jdk16u] RFR: 8258753: StartTlsResponse.close() hangs due to synchronization issues

[Prajwal Kumaraswamy]

This is a clean backport of JDK-8258753

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Commit messages:
 - Backport 415553325831b79a7e55071f6bd7c73eb1a636ec

Changes: https://git.openjdk.java.net/jdk16u/pull/95/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk16u&pr=95&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8258753
  Stats: 18 lines in 1 file changed: 8 ins; 2 del; 8 mod
  Patch: https://git.openjdk.java.net/jdk16u/pull/95.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk16u pull/95/head:pull/95

PR: https://git.openjdk.java.net/jdk16u/pull/95