Expose netId to SystemApi

Tethering will be build as unblundled APP. It can't use @hide
API anymore. Expose netId for tethering because it need to set
proxy dns server with netId.

Bug: 144758139
Test: build
Change-Id: Ifefa791940874617bb479f5c23488d14be87f45e
1 file changed
tree: 04675a916eb41b061eb7f063d85590af83b67f62
  1. core/
  2. services/
  3. tests/