Update default account preference settings dialog

Make it look like the other account picker dialogs in the app.

Test: Manual usage of default account selector in settings menu.
Tested swapping between three accounts with going back to the main
view to see if the settings stick.
Tested making a new contact would save to the proper default.

Bug: 29282755
Change-Id: Ib09d9bbe3e2cf29413e012b3aeb3218eb0782753