Do not print misleading debug messages in some scenarios.

When the mobile network is not active, querying the network
information might trigger the misleading debug messages. Added
some condition checks to prevent this.

bug: 30850733
Change-Id: Ice6d548a56f98bac7fe2ca6a06148350b505533d

core/java/android/net/NetworkIdentity.java

@@ -175,7 +175,11 @@ public class NetworkIdentity implements Comparable<NetworkIdentity> {
 
         if (isNetworkTypeMobile(type)) {
             if (state.subscriberId == null) {
-                Slog.w(TAG, "Active mobile network without subscriber!");
+                if (state.networkInfo.getState() != NetworkInfo.State.DISCONNECTED &&
+                        state.networkInfo.getState() != NetworkInfo.State.UNKNOWN) {
+                    Slog.w(TAG, "Active mobile network without subscriber! ni = "
+                            + state.networkInfo);
+                }
             }
 
             subscriberId = state.subscriberId;