Nova V2.1 API has strong input validation by making validation
through JSON schema.
This patch makes create server schema 'additionalProperties' to False
as all create server extensions are implemented in V2.1.
After this, V2.1 will not allow extra arg for create server.
This patch also fix the API sample files which were passing extra arg in
create request body.
Partially implements blueprint v2-on-v3-api
Change-Id: Ib2a4272cbacb3011b800776577233545af3d9d4b
5ba9301c34