RFR: 8326705: Test CertMsgCheck.java fails to find alert certificate_required

[Anthony Scarpino]

Hi,

I need a review for this simple change to fix a threading problem with the test. The server thread was not completing before the check occurred on the main thread.  The failure showed up in windows and macos, but not linux.  With this fix, running 100 times, windows & macos showed no failures.

Tony

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Commit messages:
 - fiddle with msgs
 - blank line
 - cleanup
 - Update
 - Add join() to Server.done()
 - remove problemlist entry

Changes: https://git.openjdk.org/jdk/pull/19553/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19553&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8326705
  Stats: 36 lines in 3 files changed: 13 ins; 5 del; 18 mod
  Patch: https://git.openjdk.org/jdk/pull/19553.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19553/head:pull/19553

PR: https://git.openjdk.org/jdk/pull/19553