Networking v2: Issue with Time Fields

The Networking resources which include CreatedAt and UpdatedAt fields cause time parsing errors with older releases of OpenStack. This is because the fields are currently set to time.Time (RFC 3339) but older OpenStack releases send the date back as an RFC 3339 "no Z" format.

The structs which include these fields need to be updated with a custom UnmarshalJSON method to handle both time formats.