Start default connections on startup.

On devices with mobile data we were kind of doing this in Telephony.
Devices without could use this.

bug:5030831
Change-Id: I9940561e88e43917bc8e638f5c3b15fced3821ae

services/java/com/android/server/ConnectivityService.java

@@ -484,6 +484,7 @@ public class ConnectivityService extends IConnectivityManager.Stub {
                 continue;
             }
             mCurrentLinkProperties[netType] = null;
+            if (mNetConfigs[netType].isDefault()) mNetTrackers[netType].reconnect();
         }
 
         IBinder b = ServiceManager.getService(Context.NETWORKMANAGEMENT_SERVICE);