Update VPN tests to mock out createAttributionContext

This allows VpnManagerServiceTest continues to work after
adding an attribution tag to VpnManagerService

Ignore-AOSP-First: This project will automerge from AOSP to
                   udc-mainline-prod but the dependency CL in
                   frameworks/base/ will not. Thus changes will be
                   merged to udc-dev first and then cherry picked
                   to AOSP
Bug: 278943609
Test: atest FrameworksNetTests:android.net.connectivity.com.android.server.VpnManagerServiceTest
Change-Id: I4228a7fb308b8d01aee53f0734f4c5753908473a
1 file changed