RFR: 8276177: nsk/jvmti/RedefineClasses/StressRedefineWithoutBytecodeCorruption failed with "assert(def_ik->is_being_redefined()) failed: should be being redefined to get here"

[Coleen Phillimore]

The boolean AND was sharing a flag with another thread, so the value of _misc_is_being_redefined was being set and reset with the other thread.  Moved the bit to AccessFlags which has space and an atomic set operation.
Tested with tier1-6, 7-8 in progress.

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Commit messages:
 - 8276177: nsk/jvmti/RedefineClasses/StressRedefineWithoutBytecodeCorruption failed with "assert(def_ik->is_being_redefined()) failed: should be being redefined to get here"

Changes: https://git.openjdk.java.net/jdk/pull/6410/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6410&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8276177
  Stats: 13 lines in 3 files changed: 7 ins; 2 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6410.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6410/head:pull/6410

PR: https://git.openjdk.java.net/jdk/pull/6410