Fix entitlement failed when device is on CBRS

When active cellular internet is switched to CBRS in DSDS case,
default data sub id may not be changed. Fix by using active
subscription id and pass this sub id to entitlement app.

Bug: 134994718
Test: atest TetherServiceTest
Test: manual test with carrer SIMs.

Change-Id: I30a1d70c0690f0dba8f4171a2bde884f9b7ccfc4

tests/unit/src/com/android/settings/wifi/tether/TetherServiceTest.java

@@ -458,7 +458,7 @@ public class TetherServiceTest extends ServiceTestCase<TetherService> {
         }
 
         @Override
-        int getDefaultDataSubscriptionId() {
+        int getActiveDataSubscriptionId() {
             return INVALID_SUBSCRIPTION_ID;
         }
     }