Fix: adding missing icons in the elastic query editor and the single stat editor. (#24914)

* fixed issue that the icon was missing in es group by.

* fixed missing icon in the single stat value mappings.

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

@@ -214,10 +214,10 @@
       </div>
       <div class="gf-form">
         <label class="gf-form-label" ng-if="$first">
-          <a class="pointer" ng-click="addFiltersQuery()"><icon class="'plus'"></icon></a>
+          <a class="pointer" ng-click="addFiltersQuery()"><icon name="'plus'"></icon></a>
         </label>
         <label class="gf-form-label" ng-if="!$first">
-          <a class="pointer" ng-click="removeFiltersQuery(filter)"><icon class="'minus'"></icon></a>
+          <a class="pointer" ng-click="removeFiltersQuery(filter)"><icon name="'minus'"></icon></a>
         </label>
       </div>
     </div>

public/app/plugins/panel/singlestat/mappings.html

@@ -20,7 +20,7 @@
   <div class="gf-form-group">
     <div class="gf-form" ng-repeat="map in ctrl.panel.valueMaps">
       <span class="gf-form-label">
-        <icon class="'times'" ng-click="ctrl.removeValueMap(map)"></icon>
+        <icon name="'times'" ng-click="ctrl.removeValueMap(map)"></icon>
       </span>
       <input
         type="text"