Block address families with routes, not NetworkAgent side channel

Now that we support unreachable routes, use those to block
address families on VPNs. This is a much more elegant solution.
Also update LinkProperties when IP addresses are added and
removed, fixing a TODO.

Bug: 17462989
Change-Id: Ib749d84710dca70d672350b9f129bb91419ec77e
2 files changed
tree: 0a40b6a2e6a6a8a5d7e6acf44d597dfcb241294f
  1. core/
  2. services/
  3. tests/