Regression on editing hook values in helper_issues_show_detail_after_setting (Bug #622)

e2d16e1397b7 fixed an API compatibility (good) but it caused a regression on the ability for a hook to edit the journal detail attributes. Short version: hooks have always been limited so they cannot change the object passed in via context but they can edit those object's attributes. So in this case a hook cannot edit detail but it can edit detail.value (by edit I mean make a change that the hook caller sees).

I've posted more details on the commit but I haven't had the time to get a fix working yet. A simple test is to create a hook and try to change an attribute in the detail object.

1SomeHookClass
2  #...
3  def helper_issues_show_detail_after_setting(context = { })
4    context[:detail].old_value = "Old value should now be changed to this hardcoded value" 
5  end
6end

(This might even be caused by AAJ but I haven't dug back through the history).