User's retain passwords when node is deleted

When a node with a password is deleted it would seem logical to remove the node's password from any users that have it, as this password now doesn't relate to anything.

But in nodeaccess_password_nodeapi in the delete op, this module only deletes from the nodeaccess_password table and not the nodeaccess_password_users table.

I am attaching a small patch for removing passwords from the nodeaccess_password_users table.

I hope I have created it correctly, let me know if not.