fix broken UT with bad api version

pom.xml

@@ -41,7 +41,7 @@
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <metamx.java-util.version>0.25.5</metamx.java-util.version>
         <apache.curator.version>2.4.0</apache.curator.version>
-        <druid.api.version>0.1.12</druid.api.version>
+        <druid.api.version>0.1.13</druid.api.version>
     </properties>
 
     <modules>

server/src/main/java/io/druid/server/coordinator/DruidCoordinatorRuntimeParams.java

@@ -205,7 +205,7 @@ public class DruidCoordinatorRuntimeParams
       this.emitter = null;
       this.stats = new CoordinatorStats();
       this.coordinatorDynamicConfig = new CoordinatorDynamicConfig.Builder().build();
-      this.balancerReferenceTimestamp = null;
+      this.balancerReferenceTimestamp = DateTime.now();
       this.strategyFactory = new CostBalancerStrategyFactory(1);
     }