Fix up android.core CTS tests.

Fix several wrongly configured tests that were either
looking for tests in the wrong jar (apache-harmony-tests
instead of core-tests) or using the wrong prefix.

Also, this change creates subsets of the harmony tests based
on subpackage names (java.net, java.io, java.nio etc.) instead
of the earlier harmony groupings.

Change-Id: Iea0e20d23512611d1aac92b2f8219031b6396c77