[jdk11u-dev] RFR: 8234608: [TESTBUG] Fix G1 redefineClasses tests and a memory leak

[Goetz Lindenmaier]

I backport this test-only change for parity with 11.0.17-oracle.

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Commit messages:
 - Backport f844943273f094d925dcb02bdc43d07c0ad9ae98

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/1093/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=1093&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8234608
  Stats: 20 lines in 8 files changed: 4 ins; 1 del; 15 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/1093.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/1093/head:pull/1093

PR: https://git.openjdk.java.net/jdk11u-dev/pull/1093