LockdownVpnTracker directly uses resources from
com.android.internal.R. This is acceptable because it's platform
code. But ConnectivityServiceTest uses the LockdownVpnTracker
built from the module source tree, and when that code fetches
resources on a previous Android release, it crashes because the
resource IDs don't exist; non-public resource IDs aren't stable.
Fix this by mocking the resources used by LockdownVpnTracker.
Test: atest ConnectivityCoverageTests
Change-Id: I239a18a38d4f1082f76f5ff1b831c15ee753bdfd
19e6171926