[jdk17u-dev] RFR: 8317188: G1: Make TestG1ConcRefinementThreads use createTestJvm

[Goetz Lindenmaier]

I backport this to improve testing in 17.

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Commit messages:
 - Backport a949824e98a8872645f292c9cc9ed2fe1cccadce

Changes: https://git.openjdk.org/jdk17u-dev/pull/2947/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=2947&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8317188
  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/2947.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/2947/head:pull/2947

PR: https://git.openjdk.org/jdk17u-dev/pull/2947