experiments: Allow pinging a percentage of nodes

refs: #3265

Change-Id: I80a37d4a8cf6ca5a25d03f1f98cdcf9394feb92f
diff --git a/ndn/experiments/failure_experiment.py b/ndn/experiments/failure_experiment.py
index 8bca445..d8d7dc9 100644
--- a/ndn/experiments/failure_experiment.py
+++ b/ndn/experiments/failure_experiment.py
@@ -36,7 +36,7 @@
         self.PING_COLLECTION_TIME_AFTER_RECOVERY = 120
 
     def run(self):
-        self.startPings()
+        self.startPctPings()
 
         # After the pings are scheduled, collect pings for 1 minute
         time.sleep(self.PING_COLLECTION_TIME_BEFORE_FAILURE)