Fix interfaces response schema

After removing v3 schemas, we have only 1 set of schemas for v2 (/v2.1)
APIs but those end up in scattered structure.

Schema files needs to be re arranged into a clean structure. Any
resource schema should be defined in single file for better readability.

This patch merge the interfaces response schema into one file
Also define the schema for show and create os-interface API.

Partially implements blueprint rearrange-nova-response-schemas

Change-Id: I4ff75ef4d29304230a85aa224e43657e96b18f2e
3 files changed