RFR: 7901757: Race in counting total number of failures from TestNG

[Jaikiran Pai]

Can I please get a review of this change which proposes to fix the issue noted in https://bugs.openjdk.org/browse/CODETOOLS-7901757?

As noted there, the current implementation in jtreg's testng test listener doesn't take into account that the callback methods on that listener instance can be invoked concurrently for different threads. As a result, the count tracking logic in the listener ends up in a race condition which results in reporting incorrect numbers.

The commit in this PR fixes that issue and introduces a self test which reproduces the race issue and verifies the fix. The new test and existing tests continue to pass with this change.

-------------

Commit messages:
 - 7901757: Race in counting total number of failures from TestNG

Changes: https://git.openjdk.org/jtreg/pull/216/files
  Webrev: https://webrevs.openjdk.org/?repo=jtreg&pr=216&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7901757
  Stats: 122 lines in 4 files changed: 103 ins; 9 del; 10 mod
  Patch: https://git.openjdk.org/jtreg/pull/216.diff
  Fetch: git fetch https://git.openjdk.org/jtreg.git pull/216/head:pull/216

PR: https://git.openjdk.org/jtreg/pull/216