Application Search - fix error updating searches from human-readable links

Summary:
Fixes T5666. When we have a pretty link right now it can conflict with form data; e.g. if you have 'statuses=open' in the URI and then uncheck status = open in the UI, you will still get the open status in the next search.

To fix this, set the form action explicitly to lose all the get parameter junk.

Test Plan: tried the test case in T5666 / this description and it no longer failed...!

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T5666

Differential Revision: https://secure.phabricator.com/D10115