RFR: 8323670: A few client tests intermittently throw ConcurrentModificationException [v2]

[Tejesh R]

> Suggested fix [JDK-8307091](https://bugs.openjdk.org/browse/JDK-8307091) also created concurrent exception intermittently (monthly once/quarterly once) on CI system. The issue was not able to be reproduced yet, hence proposing an alternative fix which uses iterators to compare the List.
> CI testing shows green.

Tejesh R has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Revert fix 8307091 + Synchronised filecache
 - Merge branch 'master' of https://git.openjdk.java.net/jdk into branch_8323670
 - Fix

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Changes:
  - all: https://git.openjdk.org/jdk/pull/17462/files
  - new: https://git.openjdk.org/jdk/pull/17462/files/7d70560b..9cf570fb

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17462&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17462&range=00-01

  Stats: 25510 lines in 669 files changed: 14131 ins; 8678 del; 2701 mod
  Patch: https://git.openjdk.org/jdk/pull/17462.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17462/head:pull/17462

PR: https://git.openjdk.org/jdk/pull/17462