Simplify test tear down

Once #17125 is resolved and we use a current version of JUnit, we should turn the tests below into a `@ParameterizedClass` and move the environment tear down into a `@AfterEach` method.

- `NetworkIsolationTest`

First check the status of #17125 and the repository's current JUnit version. Then locate NetworkIsolationTest and review its existing environment teardown. Done means the test uses @ParameterizedClass and performs environment teardown in an @AfterEach method.

Written by the indexing model from the issue text.