RFR: 8265150: AsyncGetCallTrace crashes on ResourceMark

[Coleen Phillimore]

This change seems to keep the test case in the bug from crashing in the ResourceMark destructor.  We have a ResourceMark during stack walking in AsyncGetCallTrace.  Also RegisterMap during jvmti shouldn't process oops, fix care of @fisk.
Testing tier1-6 in progress.

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Commit messages:
 - 8265150: AsyncGetCallTrace crashes on ResourceMark

Changes: https://git.openjdk.java.net/jdk/pull/6606/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6606&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8265150
  Stats: 9 lines in 2 files changed: 0 ins; 3 del; 6 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6606.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6606/head:pull/6606

PR: https://git.openjdk.java.net/jdk/pull/6606