Show "add account" dialog when it needs to appear

Don't show the dialog if the only account is not a device account.
Set the default to be the only account if it is *not* a device
account.

Test:
Manually checked:
  * Removing only account and attempting to create a new account shows
    dialog
  * Clearing preferences shows dialog
  * If dialog was canceled, verify dialog doesn't appear anymore.
  * After adding a google account, (and without manually setting default)
    verified adding a new contact did not show a dialog and the default was
    automatically set to the only account on device.
  * Having two accounts and no default shows the pick default account dialog
  * Removing multiple accounts still has the same behavior as bullet 1

Bug:32555078
Change-Id: Iec664efca7e886d7376cd2aae7c5b2bdad3a8b84