HBase tests shouldn't have to create namespace in every class

Currently all HBase test classes create/delete namespaces in their Before/After method. This cannot be easily abstracted to a common place, because:

Its difficult to move the namespace creation logic to a common place because of the following:
1. The namespace id needs to be defined in the test classes, cannot be defined in the util classes because it is used in both HBase and non-HBase tests.
2. We cannot store it in the Util class' state, because there's no state in the Util classes, their objects are constructed using a no-param constructor. So we'd have to pass it to a method in the util class and ensure we pass the same one during create/delete.
3. Adding util methods like create(), drop(), etc that automatically create the namespace and delete during drop would create problems if we had multiple tables (calling a drop would try to delete namespace, even if there are other tables in the namespace.