blogapi_metaweblog_get_category_list does not validate user

Issue Summary

blogapi_metaweblog_get_category_list does not call blogapi_validate_user and generates errors when working with authenticated users. Most (all?) of the other blogapi_* functions make this call at the beginning of the function:

$user = blogapi_validate_user($username, $password);
if (!$user->uid) {
return blogapi_error($user);
}

Adding the above code to blogapi_metaweblog_get_category_list fixes the error and the API call will return categories.