RFR: 8262443: GenerateOopMap::do_interpretation can spin for a long time.

[Robbin Ehn]

With Safepoint/Handshake timeout enabled in rare cases this methods spins for a long time, blocking safepoints/handshakes, so timeout (with a long delay) is triggered.

In some cases we are in native while executing this method and in some in vm.
That's why there is an check for state in vm.

Tested with other changes in t-1-7 this specific case of timeout is no longer an issue.
This change-set passes T1 stand alone.

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Commit messages:
 - Go to blocked when loop

Changes: https://git.openjdk.java.net/jdk/pull/2742/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2742&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8262443
  Stats: 11 lines in 2 files changed: 6 ins; 2 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2742.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2742/head:pull/2742

PR: https://git.openjdk.java.net/jdk/pull/2742