title: Context.Wait() isn't triggered by an attachment
body: <p>[Update] I verify another thing and it appears that my bot, hosted in Azure, just doesn't accept anymore any kind of attachment...</p>
  
  <p>I just update to the 3.81 version of the Bot Framework and one thing isn't working anymore.</p>
  
  <p>I expect from the user to send either a text or an attachment. So I wait for the response with <code>context.Wait(waitForAnswer)</code></p>
  
  <p>But the method <code>waitForAnswer</code> doesn't trigger if the user sends an attachment... Now if I want to receive one, it seems that the only way is using <code>PromptDialog.Attachment</code>... but this isn't fine for my use case because I don't know if the user will send an attachment or a simple text message.</p>
  
  <p>Note that within the emulator, the function <code>waitForAnswer</code> is correctly triggered by an attachment... But when I try to use Telegram channel or simply the webchat, problem rise</p>