Fix update_server JSON Schema for Nova V2

This patch fix the update_server V2 Schema to remove the
'progress' attribute from 'required' field.
'progress' attribute is not always present in response.
If server's status is one of the progress status ("ACTIVE",
"BUILD", "REBUILD", "RESIZE", "VERIFY_RESIZE",) then only
'progress' is present in response. So it should not defined as
'required'

Fixing it in base schema as same applies for other server APIs
(GET, rebuild).

This patch also adds the test case for update server in stop state
where 'progress' attribute does not come in response body.

Partially implements blueprint nova-api-attribute-test

Change-Id: Id77d263f685f69f48a8b5592465bfe91eb306443
Merge "Fix update_server JSON Schema for Nova V2"