DA receiver should be protected with BIND_DEVICE_ADMIN.

- DPM.setActiveAdmin() will not accept DAs without BIND_DEVICE_ADMIN
when it's targeting NYC or above.

- DAs without BIND_DEVICE_ADMIN targeting MNC or below will still be
accepted. (with a logcat warning)

- DAs that are already set on a device without BIND_DEVICE_ADMIN
will still be accepted regardless of the target API level, even when
it's upgraded to a version targeting NYC.

Bug 24168653

Change-Id: I1914c2ec99135d9dd8cbac3f6914f9e43bafacc8