Fixed Chargeback Rate display

Fixed code to display of Cloud/Infrastructure providers rates after Save
Code fix properly identifies any EMS as such
Refactored code for better readability

Linked similar GitHub issue to the BZ ticket

https://bugzilla.redhat.com/show_bug.cgi?id=1073083
https://github.com/ManageIQ/manageiq/issues/138#event-148990147
This whole case statement using strings to compare classes seems like a big code smell.  In a Ruby case statement, the when clauses are evaluated using the threequal or triple equal or === operator.  Some example usages are http://stackoverflow.com/questions/4527220/3-equals-or-case-equality-operator and http://stackoverflow.com/questions/5616912/ruby-triple-equal

This means that there is no point translating the object to a string and comparing strings in a case statement.  The Ruby way to do this is something like the following:

```ruby
object = @edit[:current_assignment][0][:object]
@edit[:new][:cbshow_typ] = case object
                                             when NilClass
                                                "#{@edit[:current_assignment][0][:tag][1]}-tags"
                                             when MiqEnterprise
                                                "enterprise"
                                             when EmsCluster
                                                object.class.name.underscore
                                             when ExtManagementSystem
                                                object.class.base_class.name.underscore
                                             else
                                                object.class.name.downcase
                                             end
```