Changing _wpsc_action_setup_customer to run on init instead of wp or wp_loaded.  See conversations at https://github.com/wp-e-commerce/WP-e-Commerce/commit/c5f6c7fae6acf35cc92ee7321bb30b018c85eb36 and https://github.com/wp-e-commerce/WP-e-Commerce/issues/497.  Fixes #497.