Fixed refactored code to set date and time variable based on params that came in.

Changed to set date variable from exp[exp_value_key][exp_value_index] only when params_time_key came in.

https://bugzilla.redhat.com/show_bug.cgi?id=1142711
Merge pull request #659 from h-kataria/fixed_refactored_exp_editor_date_selector

Fixed refactored code to set date and time variable based on params that...
Modify ManageIQ/Infrastructure/vm/retirement statemachine and method
classes for combining delete and unregister provider.

Class - remove unregisterfromprovider state.
Remove instance display names.
Rename delete_from_provider_check method to check_delete_from_provider
Modified delete_from_provider method to have option for delete and
unregister, added unregister code, and changed method criteria to
check for vm archived or orphaned instead of host.nil.
Modified Default instance to reflect provider changes.

https://bugzilla.redhat.com/show_bug.cgi?id=1074532