RFR: 8298992: runtime/NMT/SummarySanityCheck.java failed with "Total commi…tted (MMMMMM) did not match the summarized committed (NNNNNN)

[Afshin Zafari]

During exhaustive tests, it is observed that during taking snapshot of NMT metrics it is possible that new allocations happen concurrently, although a `ThreadCritical` is used during copying current metrics to the snapshot.
A loop is surrounding the copying and checks whether the copied and original are the same.

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Commit messages:
 - Set a limit for loop, renamed a local var.
 - Rmoved a missed log.
 - Extra log_debug are removed.
 - 8298992: runtime/NMT/SummarySanityCheck.java failed with "Total committed (MMMMMM) did not match the summarized committed (NNNNNN)"

Changes: https://git.openjdk.org/jdk/pull/15306/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15306&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8298992
  Stats: 12 lines in 1 file changed: 8 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/15306.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15306/head:pull/15306

PR: https://git.openjdk.org/jdk/pull/15306