RFR: 8282651: ZGC: vmTestbase/gc/ArrayJuggle/ tests fails intermittently with exit code 97

[Ramkumar Sunderbabu]

Fixing JuggleTests for OOME.
The JuggleTests continuously allocate memory and juggle them in various array positions. Over the course of allocation, heap might be fully filled, esp in high memory strategy. The test doesn't take into account OOME and run under the assumption that any freed memory would be immediately GCed. Immediate GC under memory stress is not guaranteed. Hence it is better to explicitly call WhiteBox API to do the job.

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Commit messages:
 - 8282651: ZGC: vmTestbase/gc/ArrayJuggle/ tests fails intermittently with exit code 97

Changes: https://git.openjdk.org/jdk/pull/9645/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9645&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8282651
  Stats: 159 lines in 34 files changed: 98 ins; 0 del; 61 mod
  Patch: https://git.openjdk.org/jdk/pull/9645.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9645/head:pull/9645

PR: https://git.openjdk.org/jdk/pull/9645