Make tasklist and taskpage use subsecond durations

appengine/swarming/ui/res/imp/tasklist/task-list-data.html

 <!--
   Copyright 2016 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.
 
   This in an HTML Import-able file that contains the definition
   of the following elements:
 
     <bot-list-data>
 
@@ skipping 239 matching lines @@
           t.tagMap = tagMap;
 
           TIMES.forEach(function(time) {
             swarming.sanitizeAndHumanizeTime(t, time);
           });
           // Running tasks have no duration set, so we can figure it out.
           if (!t.duration && t.state === this.RUNNING && t.started_ts){
             t.duration = (now - t.started_ts) / 1000;
           }
           // Make the duration human readable
-          if (t.duration){
-            t.human_duration = this._humanDuration(t.duration);
-          }
+          t.human_duration = this._humanDuration(t.duration);
         }.bind(this));
         return json.items;
       }
     });
   })();
   </script>
 </dom-module>