Refresh mFilteredRoutes when routes are changed

When a route changes its features, the returned getRoutes() can be
changed.

Bug: 159142641
Test: run support v7 demos manually to check onRouteAdded callback is
invoked

Change-Id: Icea855d631a566fd9129f98306e3ea8af4920764

media/java/android/media/MediaRouter2.java

@@ -620,6 +620,7 @@ public final class MediaRouter2 {
                     changedRoutes.add(route);
                 }
             }
+            mShouldUpdateRoutes = true;
         }
         if (changedRoutes.size() > 0) {
             notifyRoutesChanged(changedRoutes);