Sonar suggestion - use a secure random number generator

Change-Id: I28075845555bcbc384a49e07353b3192c413b8f7
diff --git a/utils/misc/src/main/java/org/onlab/graph/GAPopulation.java b/utils/misc/src/main/java/org/onlab/graph/GAPopulation.java
index 22efd84..d85bd3b 100644
--- a/utils/misc/src/main/java/org/onlab/graph/GAPopulation.java
+++ b/utils/misc/src/main/java/org/onlab/graph/GAPopulation.java
@@ -15,6 +15,7 @@
  */
 package org.onlab.graph;
 
+import java.security.SecureRandom;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
@@ -25,7 +26,7 @@
  * to run a genetic algorithm on the population and return the fittest solutions.
  */
 class GAPopulation<Organism extends GAOrganism> extends ArrayList<Organism> {
-    Random r = new Random();
+    Random r = new SecureRandom();
 
     /**
      * Steps the population through one generation. The 75% least fit