fix values_for

[aduffeck]

This commit fixes the generated values_for methods. A test for that already existed and failed with

 test: Campaign should return all defined values of a given bitmask attribute. ERROR                                                                                        
    undefined local variable or method `webprintemailphone' for #<Class:0x7f89e23cae60>

With this commit it passes again.

[plagi]

+1

[joelmoss]

cheers!