netd: bandwidth: tethering global alert support

Now, when nat is enabled/disabled it will let the bandwidthcontroller
know that it might need to add/remove the matching global alert into
the tethering rules in the FORWARD chain of iptables.

Bug: 5336638
Change-Id: I1843f3f6601f371537f754a31db792e054b36a1d
3 files changed