This eliminates the need for the ConnectivityService.VpnCallback class.
This requires shifting VPNs to the new "network" netd API.
VpnService.protect() is modified to no longer go through ConnectivityService.
NetworkCapabilities is extended to add a transport type for VPNs and a
capability requiring a non-VPN (so the default NetworkRequest isn't satisfied
by a VPN).
bug:15409918
Change-Id: Ic4498f1961582208add6f375ad16ce376ee9eb95
6bc2c2c34f