base

Fix IP address cleanup on network disconnect

We used to bring down the interface on network disconnect
which would in turn clean up all the IP addresses.

The interface bringup/shutdown is now handled by wpa_supplicant.
Add netd interface for clearing all IP addresses

Bug: 4676254
Change-Id: I7e24c0ab2e4a412b8d61e9c33ce028966913aaf6