RFR: 8307428: jstat tests doesn't tolerate dash in the O column

[Stefan Karlsson]

When running jstat tests like the following:
test/jdk/sun/tools/jstatd/TestJstatdServer.java

with Generational ZGC we get a failure because the O (old generation percentage) is reported as `-` and not a number. The reason why it is reported as `-` is that the current capacity of the old generation is zero and that leads to a divide-by-zero in this line:
https://github.com/openjdk/jdk/blob/82a8e91ef7c3b397f9cce3854722cfe4bace6f2e/src/jdk.jcmd/share/classes/sun/tools/jstat/resources/jstat_options#L1029

G1 has some workarounds for this situation where the reported capacity is slightly above 0. I'm a bit reluctant to add such a hack into Generational ZGC. I've talked to the jstat maintainers and they propose that we simply relax the test.

Tested locally by running the jstat/jstad tests in the Generational ZGC branch.

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Commit messages:
 - 8307428: jstat tests doesn't tolerate dash in the O column

Changes: https://git.openjdk.org/jdk/pull/13796/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13796&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8307428
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/13796.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13796/head:pull/13796

PR: https://git.openjdk.org/jdk/pull/13796