Allow mocking permission in TetheringServiceTest

The test will currently fail if it is run in a package that has
ACCESS_NETWORK_STATE. Add utilities to mock permissions, and mock the
ACCESS_NETWORK_STATE permission to be denied.

Bug: 187935317
Test: atest TetheringServiceTest
Change-Id: I8df5f2ac21bf0314098e8c2e5ba583676ae8ab38
2 files changed