Hide FloatingHeaderView while in Search state.

This prevents touches on the profile buttons (which were already
hidden due to the header view having alpha 0, but touches were
still registered).

Fix: 248338523
Test: Manually tap where the work profile button is before and
after this change. Before: switches to work profile. Afer: does
nothing in 0 state; otherwise launches item at that position.

Change-Id: Ie30661146d25740000d7a9cbe79234ac15347253