Call reset_column_information after defining mock model's table.

This is necessary in Rails 5 for the Model class to be able to detect
the primary key.

Author: Sam Phippen

spec/support/ar_classes.rb

@@ -13,6 +13,8 @@ def self.extended(host)
         nonexistent_model_id integer
       )
     eosql
+
+    host.reset_column_information
   end
 end