Remove usage of Context.NETWORK_STACK_SERVICE

The NetworkStack.getService() API should be used instead.

Bug: 151243982
Test: atest FrameworksNetTests TetheringTests
      Manual tethering test
Merged-In: I7855090bffbe895c8349ad4903b8f2eb55515f0b
(clean cherry-pick from internal branch)

Change-Id: If4af2846a82605e828287a9a4680d5547b76b802
1 file changed
tree: b4ead0c48ee0b7add2eb74549072ff1b3f68a5f3
  1. core/
  2. services/
  3. tests/