RFR: 8296401: ConcurrentHashTable::bulk_delete might miss to delete some objects [v7]

[Leo Korinth]

> ConcurrentHashTable::bulk_delete might miss to delete some objects if a bucket has more than 256 entries. Current uses of ConcurrentHashTable are not harmed by this behaviour. 
> 
> I modified gtest:ConcurrentHashTable to detect the problem (first commit), and fixed the problem in the code (second commit).
> 
> Tests passes tier1-3.

Leo Korinth has updated the pull request incrementally with one additional commit since the last revision:

  rerun test

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Changes:
  - all: https://git.openjdk.org/jdk/pull/10983/files
  - new: https://git.openjdk.org/jdk/pull/10983/files/b9d8b105..a4d5b80f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10983&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10983&range=05-06

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/10983.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10983/head:pull/10983

PR: https://git.openjdk.org/jdk/pull/10983