Update the subnets WADL for OpenStack Networking

Fixed these issues:
Update subnet's content is for "create subnet"
create subnet's contents is for list subnet
List subnet's contents is for show subnet

Partial-Bug: #1292359

Change-Id: Icd51ef19484a3f8780ffad2c51017b430d715bbd
author: diane fleming
Merge "Update the subnets WADL for OpenStack Networking"