Also copy-construct multinetwork policy preference

Test: as follows
    - built, flashed, booted
    - runtest frameworks-net passes
    - manual bluetooth tethering testing doesn't seem to trigger any
      actual tethering, since bt-pan interface keeps going down on
      test device (IpClient never really starts up fully)
Bug: 62476366
Bug: 113136023
Change-Id: I3265f60f8ae125eba4545cb652c95a2f70049058