config_service: change icon for force refresh to make it less ambiguous

appengine/config_service/ui/src/config-ui/config-set.html

 <!--
   Copyright 2017 The LUCI Authors. All rights reserved.
   Use of this source code is governed under the Apache License, Version 2.0
   that can be found in the LICENSE file.
 -->
 
 <link rel="import" href="config-file-card.html">
 <link rel="import" href="../../bower_components/iron-ajax/iron-ajax.html">
 <link rel="import" href="../../bower_components/iron-icons/iron-icons.html">
 <link rel="import" href="../../bower_components/paper-item/paper-item.html">
@@ skipping 86 matching lines @@
             <template is="dom-if" if="[[_not(lastImportAttempt.success)]]">
               <iron-icon id="invalid" icon="icons:warning" class="paper-red"></iron-icon>
             </template>
           </template>
           <template is="dom-if" if="[[_not(lastImportAttempt)]]">
             <iron-icon icon="icons:help" class="paper-grey"></iron-icon>
           </template>
         </template>
         <template is="dom-if" if="[[auth_headers]]">
           <paper-icon-button id="force-refresh"
-                             icon="icons:refresh"
+                             icon="icons:file-download"
                              on-tap="_forceRefresh">
           </paper-icon-button>
           <paper-tooltip for="force-refresh" offset="0">
             Re-import the config-set from the repository.
           </paper-tooltip>
         </template>
       </div>
       <div class="category">
         <p>[[_formatCategory(category)]]</p>
         <template is="dom-if" if="[[_not(isLoading)]]">
@@ skipping 172 matching lines @@
           this.errorMessage = "Internal server error.";
         } else {
           this.errorMessage = "Error occured. Try again later.";
         }
         this.fire('fetchError');
       }
 
     });
   </script>
 </dom-module>