title: Coupon code Magento 1.9.x bug
body: <p>I have two users: A and B <br/>
  <strong>A</strong>: checkout with Paypal<br/>
  <strong>B</strong>: checkout with COD<br/>
  They apply coupon code: XXXXABC</p>
  
  <p>In Admin Setting:<br/>
  <strong>Uses per Coupon</strong>: set to <strong>1</strong>.</p>
  
  <p>However,<br/>
  user A in <strong>Payment Review</strong> (Paypal Review)<br/>
  use B in <strong>Order Review</strong>.<br/>
  User A and B click <strong>Place Order</strong> at the same time (or late seconds). Both of them applied XXXXABC coupon code. But, <strong>Uses per Coupon</strong>: set to <strong>1</strong> in Admin.<br/></p>
  
  <p><strong>Expect result</strong>: Only one user can apply this coupon code.
  Any idea about this issue?</p>