RFR: 8352994: ZGC: Fix regression introduced in JDK-8350572

[Stefan Karlsson]

We have seen a bunch of timeouts that all points towards the introduction of a check against VMError::is_error_reported_in_current_thread() in the ZGC verification code. I propose this workaround to first check if there's really an error reporting event that is going on by checking VMError::is_error_reported().

The underlying performance issue (or hang(?)) when calling os::current_thread_id() is being investigated as a separate bug. This fix just tries to clean up issues we see when running ZGC testing.

Thanks to @plummercj for digging into this and proposing the same workaround.

Testing: GHA is clean, I'll run this through a few tiers of our CI pipeline

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Commit messages:
 - 8352994: ZGC: Fix regression introduced in JDK-8350572

Changes: https://git.openjdk.org/jdk/pull/24349/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24349&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8352994
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/24349.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24349/head:pull/24349

PR: https://git.openjdk.org/jdk/pull/24349