Perform the quit action and kill the *Kill Ring* buffer earlier.

Previously the `*Kill-Ring*` buffer is only closed after the item has been inserted and the highlighting has finished (if highlighting of the inserted item is turned on), this takes 0.5 seconds, and gives a user experience that appears unresponsive; they ask for insert and close buffer, but the buffer takes does not close immediately.

After this patch when the user asks for insert and exit, we first establish what will be inserted, then we close the `*Kill Ring*` buffer, and then we insert and highlight the item.   The result is, I believe, a user experience that "feels" more responsive.

This obviously only makes a difference for the case where the user makes use of the functions like `browse-kill-ring-insert-and-quit`, in other cases, like `browse-kill-ring-insert` where the `*Kill Ring*` buffer is left open there should be no visible change to the user.