Redirect user to admin/pifr when initiating a test via the testbot manual test form

The current UX is:
1. Submit the form
2. Watch the browser churn for 45 minutes while the test is run.

Redirecting the user to admin/pifr would allow them to view the current review status ... especially in combination with #1233210: Add javascript auto-refresh to admin/pifr "active review status" fieldset on testbots.