dns cache per interface iteration 2

name server addresses are read from the dns
cache associated wih the interface on which
the request shall be done.

processes which has requested to issue dns request
using specific interface are now proxied to netd.

added methods to attach/detach a process to a specific
dns cache/interface.

added getaddrinfoforinface method which takes an
interface as an argument.

Change-Id: I851ec8ab8ce3112626ad2a729078b91d013f32fd
13 files changed