Make KeystoreManagementTests work in the docker case

[williamrandolph]

While I was working on #32691, we added some Docker packaging tests. Right now, some of the keystore tests are failing on the distroTest.default-docker task, e.g. :qa:os:centos-6:distroTest.default-docker.

Ideally, the keystore management tests can be flexible enough to run even in the docker case. If not, the tests should be fixed so that they don't run for that docker testing task.

Relates #32691

[elasticmachine]

Pinging @elastic/es-core-infra (:Core/Infra/Packaging)

[pugnascotia]

@williamrandolph let me know if I can help here.

[williamrandolph]

@pugnascotia OK, I'm looping back around to this now.

Right now we have a PackagingTestCase class that all of the more specific test classes inherit from. Almost all of those classes either exclude Docker explicitly or select a specific packaging type other than Docker. The one exception? DockerTests, which extends PackagingTestCase but modifies the setup before each test by setting the Shell object to a new DockerShell and setting the installation object with runContainer.

If I want to make the KeystoreManagementTest class run correctly for Docker, it seems like I would have to push that Docker-specific shell/installation setup into the PackagingTestCase class. Is that something you tried doing while you were writing these test cases? Do you think there's any reason that approach wouldn't work in principle?

[pugnascotia]

I didn't try that approach, but it certainly sounds reasonable. If you run into any issues, let me know and we'll figure it out.

[williamrandolph]

Closed by #50610