title: How to disable LoadMask on GridPanel
body: <p>I've a GridPanel which is updated every 10 seconds.</p>
  
  <pre><code>var refreshEnvironmentsStoreTask = {
      run: function() {
          this.getEnvironmentsStore().load()
      },
      scope: this,
      interval: 10000 //10 second
  }
  Ext.TaskManager.start(refreshEnvironmentsStoreTask);
  </code></pre>
  
  <p>As result of frequent updates on the grid appears flicker. I want to disable LoadMask but next code doesn't work:</p>
  
  <pre><code>Ext.define('MyGrid' ,{
      extend: 'Ext.grid.Panel',
      store : 'Environments',
      viewConfig: {
          loadMask: false
      }
  });
  </code></pre>