[11u] RFR: 8228967: Trust/Key store and SSL context utilities for tests

[Lindenmaier, Goetz]

Hi,

I would like to bring this test-only change to 11.0.9.

This applies clean except for two trivial resolves:

Previously, when downporting "8234728: Some security tests should 
support TLSv1.3", I had to resolve NullHostnameCheck.java because
this change was missing. Now, bringing this to 11u, I had to resolve the
same location again now, obviously.

Further, I had to resolve the copyright in PacketLossRetransmission.java.

http://cr.openjdk.java.net/~goetz/wr20/8228967-ssl_test_utilities-jdk11/01/

Please review.
https://bugs.openjdk.java.net/browse/JDK-8228967
https://hg.openjdk.java.net/jdk/jdk/rev/d80e4bce4588

Best regards,
  Goetz.