Allow setting a Device Owner via ADB on unprovisioned device with preinstalled account

Some devices come from carriers with a preinstalled account. This
means that we couldn't set a device owner via "adb shell dpm"
commands, while the regular device owner flow worked (as the
latter just checked whether the device was provisioned).

Bug: 18354022
Change-Id: I9a677de9d34d073e218b9179ec4b0f5b4b82adc9