RFR: 8268283: serviceability/sa/TestJmapCore.java failed with zgc on linux-aarch64 after JDK-8266957

[Yasumasa Suenaga]

We still see the problem in TestJmapCore.java even though [JDK-8266957 was fixed](https://github.com/openjdk/jdk/commit/7e41ca3da820650e16d9ca7f5b188628cd666419).

According to JBS, the problem suffers on linux-aarch64 only, and I've not yet reproduce it on Linux x64, so it is difficult to fix quickly. So I added it to ProblemList-zgc.txt .

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Commit messages:
 - Update issue number
 - 8268283: serviceability/sa/TestJmapCore.java failed with zgc on linux-aarch64 after JDK-8266957

Changes: https://git.openjdk.java.net/jdk/pull/4372/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4372&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8268283
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4372.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4372/head:pull/4372

PR: https://git.openjdk.java.net/jdk/pull/4372