only rotate consumers if there are consumers to rotate!

git-svn-id: https://svn.apache.org/repos/asf/incubator/activemq/trunk@476093 13f79535-47bb-0310-9956-ffa450edef68

activemq-core/src/main/java/org/apache/activemq/broker/region/policy/RoundRobinDispatchPolicy.java

@@ -66,6 +66,7 @@ public class RoundRobinDispatchPolicy implements DispatchPolicy {
             
             // Rotate the consumer list.
             try {
+                if (consumers.size() > 1)
                     consumers.add(consumers.remove(0));
             } catch (Throwable bestEffort) {
                 log.error("Caught error rotating consumers",bestEffort);