RFR: 8286045: Use ForceGC for cleaner test cases

[Xue-Lei Andrew Fan]

Hi,

May I have the test case update reviewed?

This patch is trying to use ForceGC for cleaner test cases.  As would make the test more stable and easier to maintain.

Thanks,
Xuelei

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Commit messages:
 - 8286045: Use ForceGC for cleaner test cases

Changes: https://git.openjdk.java.net/jdk/pull/8885/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8885&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8286045
  Stats: 57 lines in 3 files changed: 19 ins; 28 del; 10 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8885.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8885/head:pull/8885

PR: https://git.openjdk.java.net/jdk/pull/8885