Test VpnProfile is not modified in startLegacyVpn

The profile is modified within startLegacyVpnPrivileged(), e.g.
ipsecCaCert, ipsecUserCert. This causes subsequent calls from
callers such as LockdownVpnTracker to fail.

Add a new test to ensure the VpnProfile is not modified in
startLegacyVpn.
Add testClone in VpnProfileTest.

Bug: 190572822
Bug: 309591931
Test: atest FrameworksNetTests, test before and after fix.
Test: Manual test
Change-Id: Id090e0dd3b9e74a7461ae90e68c41e802b458744

tests/unit/java/com/android/server/connectivity/VpnTest.java

@@ -3131,6 +3131,20 @@ public class VpnTest extends VpnTestBase {
         startPptp(false /* useMppe */);
     }
 
+    @Test
+    public void testStartLegacyVpnModifyProfile_TypePSK() throws Exception {
+        setMockedUsers(PRIMARY_USER);
+        final Vpn vpn = createVpn(PRIMARY_USER.id);
+        final Ikev2VpnProfile ikev2VpnProfile =
+                new Ikev2VpnProfile.Builder(TEST_VPN_SERVER, TEST_VPN_IDENTITY)
+                        .setAuthPsk(TEST_VPN_PSK)
+                        .build();
+        final VpnProfile profile = ikev2VpnProfile.toVpnProfile();
+
+        startLegacyVpn(vpn, profile);
+        assertEquals(profile, ikev2VpnProfile.toVpnProfile());
+    }
+
     private void assertTransportInfoMatches(NetworkCapabilities nc, int type) {
         assertNotNull(nc);
         VpnTransportInfo ti = (VpnTransportInfo) nc.getTransportInfo();