create a new ping object for each ping attempt

bubble-server/src/main/java/bubble/service/device/FlexRouterService.java

@@ -47,7 +47,7 @@ public class FlexRouterService extends SimpleDaemon {
 
     public static boolean pingFlexRouter(FlexRouter router) {
         final String prefix = "pingRouter(" + router + "): ";
-        final HttpRequestBean request = new HttpRequestBean(POST, router.pingUrl(), json(router.pingObject()));
+        final HttpRequestBean request = new HttpRequestBean(POST, router.pingUrl());
         for (int i=0; i<MAX_PING_TRIES; i++) {
             sleep(PING_SLEEP_FACTOR * i, "waiting to ping flexRouter");
             if (i == 0) {
@@ -56,6 +56,7 @@ public class FlexRouterService extends SimpleDaemon {
                 if (log.isWarnEnabled()) log.warn(prefix+"attempting to ping again (try="+(i+1)+"/"+MAX_PING_TRIES+")");
             }
             try {
+                request.setEntity(json(router.pingObject()));
                 final HttpResponseBean response = HttpUtil.getResponse(request);
                 if (!response.isOk()) {
                     log.error(prefix+"response not OK: "+response);