Update updatecheck.py

Check for the addition of an icon_hash key in a package plist. If the key is present and matches a hash of an icon that has already been downloaded no attempt will be made to download the icon again. If the icon_hash is not present or the hash does not match the behavior will revert back to normal.
Why should they already be present? I think this is wrong.
Consider: machine has Photoshop CS4 installed, and it was installed two years ago. Now you instruct Munki to remove it. Why would it have cached an icon for it?