RFR: 8300268 : ServerImpl allows too many idle connections when using sun.net.httpserver.maxIdleConnections

Fri Feb 3 18:04:55 UTC 2023

Currently there is a race condition that can allow for too many 'idleConnections' in `ServerImpl`

This PR adds a lock to make sure only one connection can be marked Idle at a time as well as a test that consistently failed before the change but which now passes.

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Commit messages:
 - updated copyright year
 - small cleanup
 - prevent too many idleConnections being allowed at once

Changes: https://git.openjdk.org/jdk/pull/12413/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12413&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8300268
  Stats: 213 lines in 3 files changed: 208 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/12413.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12413/head:pull/12413

PR: https://git.openjdk.org/jdk/pull/12413