Only leave one default network up at a time.

If original refuses to tear down, tear down new one.  It's better
to have none (which will try to launch them all again) than two.

Really people shouldn't refuse the teardown request.

bug:4183397
Change-Id: I54ea1bf0d2cd2ef16fcf2eafc69895ad2fe33ffd
diff --git a/services/java/com/android/server/ConnectivityService.java b/services/java/com/android/server/ConnectivityService.java
index 6694dbe8..8f0816d 100644
--- a/services/java/com/android/server/ConnectivityService.java
+++ b/services/java/com/android/server/ConnectivityService.java
@@ -1266,6 +1266,7 @@
                             " teardown");
                     if (!teardown(otherNet)) {
                         Slog.e(TAG, "Network declined teardown request");
+                        teardown(thisNet);
                         return;
                     }
                     if (isFailover) {