RFR: 8297798: Timeout with DTLSOverDatagram test template

[Matthew Donovan]

This fix is intended to address various time-out errors in tests that use DTLSOverDatagram as a test template. Based on test output from those bugs (JDK-8202059, JDK-8249562, JDK-8280185, JDK-8280186, JDK-8269887, JDK-8268899), this fix:

* refactors the class to only create one additional thread
* adds a CountdownLatch so if the server thread doesn't start for some reason, it is reported quickly
* cleans up code to remove a loop condition that never fired: tests always time-out before too many loop iterations
* removes CipherSuite.java from ProblemList

Ran the following tests 200 times each with no failures.
* open/test/jdk/javax/net/ssl/DTLS/ClientAuth.java
* open/test/jdk/javax/net/ssl/DTLS/PacketLossRetransmission.java
* open/test/jdk/javax/net/ssl/DTLS/RespondToRetransmit.java
* open/test/jdk/javax/net/ssl/DTLS/InvalidCookie.java
* open/test/jdk/javax/net/ssl/DTLS/CipherSuite.java

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Commit messages:
 - Merge branch 'master' into dtls
 - 8297798: Timeout with DTLSOverDatagram test template

Changes: https://git.openjdk.org/jdk/pull/11558/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11558&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8297798
  Stats: 120 lines in 2 files changed: 38 ins; 47 del; 35 mod
  Patch: https://git.openjdk.org/jdk/pull/11558.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11558/head:pull/11558

PR: https://git.openjdk.org/jdk/pull/11558