RFR: 8274888: Dump "-DReproduce=true" to the test VM command line output

[Christian Hagedorn]

When trying to rerun a failure of the test VM, one can copy the test VM command line printed to the output and directly use that one. But this requires to additionally set `-DReproduce=true` to mock the driver VM. This patch improves the manual work of adding `-DReproduce=true` and dumps it now automatically as part of the command line printed on failures.

Thanks,
Christian

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Commit messages:
 - 8274888: Dump "-DReproduce=true" to the test VM command line output

Changes: https://git.openjdk.java.net/jdk/pull/6039/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6039&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8274888
  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6039.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6039/head:pull/6039

PR: https://git.openjdk.java.net/jdk/pull/6039