networking: Fully fix requests failing when turning network off and on facebook#19709.

The previous commit partially fixed facebook#19709 by evicting all idle
connections on DISCONNECT and CONNECTING events. To fully fix facebook#19709, also
cancel all ongoing calls on these events. Cancel the ongoing calls
before evicting all idle connections, because cancelling the ongoing
calls can result in more idle connections.

Author: roberthoenig

ReactAndroid/src/main/java/com/facebook/react/modules/network/OkHttpClientProvider.java

@@ -85,6 +85,7 @@ public void onReceive(Context context, Intent intent) {
         final Thread thread = new Thread() {
           public void run() {
               for (OkHttpClient client: sClients) {
+                client.dispatcher().cancelAll();
                 client.connectionPool().evictAll();
               }
               result.finish();