[jdk11u-dev] RFR: 8281628: KeyAgreement : generateSecret intermittently not resetting

[Goetz Lindenmaier]

I backport this for parity with 11.0.17-oracle.

I had to adapt the copyright in DHKeyAgreement.java
and change hex printing in the test.
Test fails without the fix and passes with the fix.

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Commit messages:
 - Backport 1485883c9e6e24315bb21f20604b1c326e862a5b

Changes: https://git.openjdk.org/jdk11u-dev/pull/1145/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=1145&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8281628
  Stats: 103 lines in 2 files changed: 102 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1145.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev pull/1145/head:pull/1145

PR: https://git.openjdk.org/jdk11u-dev/pull/1145