hack for state_machine/rails-4.2 compatibility

state_machine overrides `column_defaults` but as of rails 4.2 it
needs to override `default_attributes` to get the same behaviour.

Ideally we need to figure a less hacky / dangerous way to set default
initial states for the machine.

current rails edge / rails 4.1.6:

https://github.com/rails/rails/blob/c4767e13d4ae927e6d605cad3846c9807745b883/activerecord/lib/active_record/core.rb#L264
https://github.com/rails/rails/blob/v4.1.6/activerecord/lib/active_record/core.rb#L186
Another try on fixing `state` fields persistence

Previous hack worked for initialization but for some reason `state`
value was not being persisted, this hack should probably lead to less
code and overrides