Clear notif upon bad wifi off + tests for bad wifi notif

If a notification is up and the avoid bad wifi setting
is turned off, the notification should disappear.

This patch also adds some general tests for the bad wifi
notifications.

Test: new tests in this patch
Change-Id: I5bc42afbe0efd93cfb59a759bf0aaba49a4bfc9f

service/src/com/android/server/ConnectivityService.java

@@ -5083,8 +5083,14 @@ public class ConnectivityService extends IConnectivityManager.Stub
     private void updateAvoidBadWifi() {
         ensureRunningOnConnectivityServiceThread();
         // Agent info scores and offer scores depend on whether cells yields to bad wifi.
+        final boolean avoidBadWifi = avoidBadWifi();
         for (final NetworkAgentInfo nai : mNetworkAgentInfos) {
             nai.updateScoreForNetworkAgentUpdate();
+            if (avoidBadWifi) {
+                // If the device is now avoiding bad wifi, remove notifications that might have
+                // been put up when the device didn't.
+                mNotifier.clearNotification(nai.network.getNetId(), NotificationType.LOST_INTERNET);
+            }
         }
         // UpdateOfferScore will update mNetworkOffers inline, so make a copy first.
         final ArrayList<NetworkOfferInfo> offersToUpdate = new ArrayList<>(mNetworkOffers);