title: Extjs remote combo validation issue
body: <p>HI,
      i am using extjs 3.2.1 lib and iam new to extjs,</p>
  
  <pre><code>I have implemented combobox with remote with filtering option in the form, i have added forceSelection(true) property to combo for validate the text with store collection and allowblank(false) to combo for enable form save button .
  </code></pre>
  
  <p>My problem is forceSelection property validates the control on the blur event only and clear the combo text , If the user enter the invalid text in the combo the save button is enabled(since i am only checked the allowblank(false) for combo) in the form, and when he hit the save button its gets submitted with invalid text in the combo.</p>
  
  <p>I have checked the isvalid() method of form and combo also, inside the save event it also returning the 'true'.</p>
  
  <p>How can i validate in this particular scenario ? </p>