Make search behave correctly

- call setIconifiedByDefault(true) and setIconified(false) to
  show magnifying glass icon inside SearchView's edit text
- manually call onActionViewExpanded() on entering search mode
  and onActionViewCollapsed() on exitting the mode to make
  SearchView work correctly with its close button
-- Those should be called automatically if we let search view
   menu item do that, but because we're using custom layout,
   we need to do that manually.
- clear focus and hide soft key when the user presses "done" button
  on soft keyboard
- ignore close event when text is empty, to prevent recursive
  exitSearchUi() call

Bug: 5080181
Change-Id: I4b603cca8e3051a247a858573ec3f6d631d75ec0