By default policy configuration, only administrative users can retrieve IP availability. Otherwise, Not Found (404) will be returned
Closes-Bug: #2003303
Change-Id: I9e3232dc5828208d3ef08b033d953501fe93fed8
1. Support subnet detail page: base info tab && ports tab
2. Refactor subnet codes: adjust a more reasonable directory structure
3. Update port related code to support ports list in the subnet detail page
4. Update port detail back to the list page: entering from the instance/network/subnet detail page will return to the instance/network/subnet detail page
5. In the instance detail interface tab, remove the device owner filter
Change-Id: I02edd0cb54a76f6b590411be5f93b57bb89c6cd6
