show pipeline agg source for derivative

public/app/plugins/datasource/elasticsearch/partials/metricAgg.html

@@ -34,7 +34,7 @@
 
 <div class="tight-form" ng-if="showOptions">
 	<div class="tight-form-inner-box">
-		<div class="tight-form last" ng-if="agg.type === 'moving_avg'">
+		<div class="tight-form last" ng-if="agg.pipelineAgg !== undefined">
 			<ul class="tight-form-list">
 				<li class="tight-form-item">
 					Based on