Check all test classes in :janusgraph-test:main that are referenced in a real test

I found that `GraphDatabaseConfigurationInstanceIdTest.java` is never executed because it is located in the :janusgraph-test:main and not in :janusgraph-test:test.
Therefore we should check all test classes :janusgraph-test:main.

Start with GraphDatabaseConfigurationInstanceIdTest.java in :janusgraph-test:main and inspect how the :janusgraph-test:main test classes are referenced by real tests. Determine which classes are not executed by the test source set, then verify that every referenced test class is covered by the appropriate test setup.

Written by the indexing model from the issue text.