[jdk11u-dev] RFR: 8317343: GC: Make TestHeapFreeRatio use createTestJvm

[Andrew Lu]

I backport this for parity with 11.0.25-oracle.

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Commit messages:
 - Backport c64bd3d6715304accd9a1e3266edd9d3d2353273

Changes: https://git.openjdk.org/jdk11u-dev/pull/2893/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2893&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8317343
  Stats: 3 lines in 1 file changed: 1 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2893.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2893/head:pull/2893

PR: https://git.openjdk.org/jdk11u-dev/pull/2893