ndn: bug fixes in nfdc and experiments

Change-Id: I8cb9b0a9e53e0319e3f18ab6a52867d406a31fd5
diff --git a/ndn/experiments/failure_experiment.py b/ndn/experiments/failure_experiment.py
index b25cbfe..a27b0a6 100644
--- a/ndn/experiments/failure_experiment.py
+++ b/ndn/experiments/failure_experiment.py
@@ -23,6 +23,7 @@
 
 from ndn.experiments.experiment import Experiment
 from ndn.nlsr import Nlsr
+from ndn.apps.ndn_ping_client import NDNPingClient
 
 import time
 
@@ -57,7 +58,7 @@
 
                 for other in self.net.hosts:
                     if host.name != other.name:
-                        self.ping(host, other, self.PING_COLLECTION_TIME_AFTER_RECOVERY)
+                        NDNPingClient.ping(host, other, self.PING_COLLECTION_TIME_AFTER_RECOVERY)
 
         # Collect pings for more seconds after CSU is up
         time.sleep(self.PING_COLLECTION_TIME_AFTER_RECOVERY)