Admin pages aren't fully rendered unless you have administer permissions

When the uc_product_keys_list_form and uc_product_keys_list_sequences_form forms are themed
drupal_render($form) only gets called if you are an administrator.

This means if another module wants to add something to this form it will not appear unless it overrides
the theme function too, which is not ideal.

Because the check for admin is already done in the form function when adding elements it isn't needed when theming.

This patch addresses this issue.