Draw main search border around button also

Summary: Extends the focus highlight around the button on main search bar as well as input.

Test Plan: reviewed on desktop and mobile breakpoints. did a search. woo.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D12364