[jdk11u-dev] RFR: 8300272: Improve readability of the test JarWithOneNonDisabledDigestAlg

[Amos]

- Backport of [JDK-8300272](https://bugs.openjdk.org/browse/JDK-8300272)
- Test succeeded in local dev box

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Commit messages:
 - Backport cf46004f276293ce8b092fe17ae579cbe45914a2

Changes: https://git.openjdk.org/jdk11u-dev/pull/2182/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2182&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8300272
  Stats: 91 lines in 1 file changed: 41 ins; 8 del; 42 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2182.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2182/head:pull/2182

PR: https://git.openjdk.org/jdk11u-dev/pull/2182