[vcloud_director] Change input options structure.

  #put_guest_customization_section_vapp
  #put_network_connection_system_section_vapp

Although no longer documented, the previous options structure is still
accepted and is mutated into the new structure. This behaviour is likely
to be deprecated at some point.
[vcloud_director] improoved tests for #ensure_list!
Merge pull request #2288 from alphagov/improved_tests_for_ensure_list

[vcloud_director] improved tests for #ensure_list!
Merge pull request #2280 from nosborn/vcloud_director_put_sections

[vcloud_director] Change input options structure.