[NS D02] Mix in the ignore on wifi policy.

Ultimately ConnectivityService and its satellites should mix in
some measurements to NetworkScore, but in the immediate future
they'll just use this to mix in at the new format the policy it
used to managed in an ad-hoc way.

As a first mix-in, this adds mixing in the IGNORE_ON_WIFI policy,
which so far used to be handled in Connectivity as the avoidBadWifi
bit. Ultimately this should move to Telephony.

Bug: 113554781
Test: ConnectivityServiceTest
Change-Id: I4869d5eb9ea74679e57c087005ed3d9b8119fed2