RFR: 8228442: DHKeyExchange/LegacyDHEKeyExchange.java failed due to "SSLException: An established connection was aborted by the software in your host machine"

[Fernando Guallini]

Test DHKeyExchange/LegacyDHEKeyExchange.java has been seen to fail intermittently. There is a thread synchronisation issue that is fixed by:

- Using SSLSocketTemplate that handles client/server socket configuration and synchronisation before connection
- Making use of a CountDownLatch and socket linger to facilitate the socket to close gracefully after both ends have finished the transmission

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Commit messages:
 - add linger-on-close
 - LegacyDHEKeyExchange uses SSLSocketTemplate, fix intermittent failure

Changes: https://git.openjdk.java.net/jdk/pull/3622/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3622&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8228442
  Stats: 287 lines in 1 file changed: 14 ins; 252 del; 21 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3622.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3622/head:pull/3622

PR: https://git.openjdk.java.net/jdk/pull/3622