Temporarly revert "In permitted_attributes, switch from database colu…

…mn detection to Rails attributes detection. Fixes #838"

This reverts commit 530a202.

Reason: Adjust tests to obtain a before and after picture

lib/cancan/ability/strong_parameter_support.rb

@@ -31,7 +31,7 @@ def get_attributes(rule, subject)
         klass = subject_class?(subject) ? subject : subject.class
         # empty attributes is an 'all'
         if rule.attributes.empty? && klass < ActiveRecord::Base
-          klass.attribute_names.map(&:to_sym) - Array(klass.primary_key)
+          klass.column_names.map(&:to_sym) - Array(klass.primary_key)
         else
           rule.attributes
         end