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. ------------- 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
