Stop using deprecated Connectivity changed broadcast.

As part of an effort to stop using deprecated APIs from Connectivity
Manager, this first CL moves away from "connectivity changed"
broadcasts, and uses APIs with callbacks.
At this point the API requestRouteToHost() is still in use, until the
GPS HAL API is updated.

Bug: 21610393
Change-Id: I425225b7ff533cb12876f29fbbfb11d3baec8dec