title: Checkbox doesn't get selected in ExtJS 4.1
body: <p>I load form data from server and filling form with it.</p>
  
  <pre><code>    var form = this.getPForm().getForm().load({
          url: '/url',
          params: {
              id: record.get('id'),
          },
      });
  </code></pre>
  
  <p>All goes OK except one checbox, which doesn't get checked even its input data is <code>true</code></p>
  
  <pre><code>            {
                  fieldLabel: 'name',
                  name: 'name',
                  minLength: 5,
                  maxLength: 80,
              }, {
                  xtype: 'checkbox',
                  fieldLabel: 'Yes?',
                  name: 'yes',
                  inputValue: '1',
                  uncheckedValue: '0',
                      listeners:{                 
                      change:function(c){
  
                          alert(c.getValue());
  
                      }
                  },
              }, 
  </code></pre>
  
  <p>On Form load I get <code>true</code> alert message informing that form data has acheved <code>checkbox</code> and is changing. But checkbox doesn't get checked!</p>