aggregator_test output includes drupal page content

The aggregator_test_feed function has "print $feed;" which outputs RSS. It also brings several Drupal content blocks which is incorrect behavior. If you add "exit;" after "print $feed;" it fixes the problem.

I don't know if this is a) an aggregator problem or b) a core problem where page output should cease after printing begins. If we just need to add "exit;" I can submit a patch.