RFR: 8370956: ShortcutHintTest test fails when executed locally on Linux

[Alexey Semenyuk]

Don't verify icons when the test package is uninstalled.

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Commit messages:
 - LinuxHelper: fix a regression from JDK-8370100

Changes: https://git.openjdk.org/jdk/pull/28064/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28064&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8370956
  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/28064.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28064/head:pull/28064

PR: https://git.openjdk.org/jdk/pull/28064