[jdk15u-dev] RFR: 8244602: Add JTREG_REPEAT_COUNT to repeat execution of a test

[Yuri Nesterenko]

I'd like to port this useful and apparently not risky enhancement which is already in other update releases.
Fix was easy to apply manually.

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Commit messages:
 - Backport b2638e5efd3c2b1abe790ab59baf28afa308614f

Changes: https://git.openjdk.java.net/jdk15u-dev/pull/203/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk15u-dev&pr=203&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8244602
  Stats: 28 lines in 3 files changed: 27 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk15u-dev/pull/203.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk15u-dev pull/203/head:pull/203

PR: https://git.openjdk.java.net/jdk15u-dev/pull/203