Local test followup

[alexeysemenyukoracle]

Fix issues uncovered in the tests after local test runs with the installation of test packages:

• LinuxHelper: fix a regression from JDK-8354988. Before the JDK-8354988 fix, when a process started with Executor didn't write to stdout, Executor.executeAndGetFirstLineOfOutput() returned an empty string; after the fix, it throws an exception.
• Fix EmptyFolderTest: when an MSI is installed, it can create empty directories. Empty directories are not created only when it is unpacked. We probably never ran EmptyFolderTest in "install test packages" mode; we always executed it in "unpack test packages" mode.
• Fix PackageTest.Group to make it work correctly when a test runs jpackage to produce both exe and msi packages, and when they are installed.

Before the fix, the sequence was:

for (action in {create, install, uninstall}) {
  for (test in tests) {
    for (type in {exe, msi}) {
      run $action on $test of $type
    }
  }
}

After the fix, the sequence is:

for (type in {exe, msi}) {
  for (action in {create, install, uninstall}) {
    for (test in tests) {
      run $action on $test of $type
    }
  }
}

Additionally:

• Add missing @Test annotation in PathGroupTest;
• Fix typo in PListReaderTest: STRING_ARRY -> STRING_ARRAY;
• Optimize RuntimeImageTest to not run jlink if external Java runtime is supplied;
• Add a test to RuntimeImageTest to verify jpackage strips the "jmod" directory and the "src.zip" file from an external runtime image

---

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