RFR: 8273217: Make ParHeapInspectTask _safepoint_check_never

[Coleen Phillimore]

Make lock be declared as safepoint_check_never.
Ran tier1-3 tests and test that uses this code: serviceability/dcmd/gc/ClassHistogramTest.java

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Commit messages:
 - 8273217: Make ParHeapInspectTask _safepoint_check_never

Changes: https://git.openjdk.java.net/jdk/pull/5323/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5323&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8273217
  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5323.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5323/head:pull/5323

PR: https://git.openjdk.java.net/jdk/pull/5323