Mock Vpn.setLockdown()

Call setRequireVpnForUids directly to enable lockdown instead of
calling the real Vpn method.

Bug: 230548427
Test: atest FrameworksNetTests
Change-Id: I91ec59f7542d145e9250a7e7a414593db3d99424

tests/unit/java/com/android/server/ConnectivityServiceTest.java

@@ -10206,7 +10206,8 @@ public class ConnectivityServiceTest {
         // Init lockdown state to simulate LockdownVpnTracker behavior.
         mCm.setLegacyLockdownVpnEnabled(true);
         mMockVpn.setEnableTeardown(false);
-        mMockVpn.setLockdown(true);
+        final Set<Range<Integer>> ranges = UidRange.toIntRanges(Set.of(PRIMARY_UIDRANGE));
+        mCm.setRequireVpnForUids(true /* requireVpn */, ranges);
 
         // Bring up a network.
         final LinkProperties cellLp = new LinkProperties();