RFR: 8291830: jvmti/RedefineClasses/StressRedefine failed: assert(!is_null(v)) failed: narrow klass value can never be zero

[Coleen Phillimore]

This has verification code that I'm going to remove so we can backport this.

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Commit messages:
 - remove verification code.
 - 8291830: jvmti/RedefineClasses/StressRedefine failed: assert(!is_null(v)) failed: narrow klass value can never be zero

Changes: https://git.openjdk.org/jdk/pull/11444/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11444&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8291830
  Stats: 21 lines in 5 files changed: 9 ins; 4 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/11444.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11444/head:pull/11444

PR: https://git.openjdk.org/jdk/pull/11444