Correct bad context path when doing pattern search inside a repository

Summary:
Ref PHI101. It looks like this was maybe copy/pasted by mistake in recent design refactoring.

We need to pass the full path, not the basename() of the path, to the search form.

Test Plan: Searched inside scripts/test/, found results inside scripts/test/.

Reviewers: amckinley

Reviewed By: amckinley

Differential Revision: https://secure.phabricator.com/D18664