Mock onUserAdded() and onUserRemoved()

Replace calls to onUserAdded() and onUserRemoved() to their
equivalent setUids() or setRequireVpnForUids() calls.

Note coverage for the calls to Vpn were added in VpnTest.

Bug: 230548427
Test: atest FrameworksNetTests
Change-Id: Ifa895f71f78bd3376216fd2759c7a5a33cd3aff1
1 file changed