Loader tests are broken

Note that these tests are some of the last tests which still need to be ported to use the Cli fixture from testutils...

When running:

./setup.py test --addoptps 'tests/loader/'

The tests consistently fail with an assertion because the Platform instance has not been created. This is expected because these tests do not use a Pipeline object, which is what currently instantiates the platform.

This is also an indicator that we do not clean up state properly between tests, the only reason these tests are passing is because the Platform has been instantiated in a previous test.

These tests dont need to be fixed (they need to be ported to use the proper fixtures), but we would do well to clean up state better in between tests.