Fix schema for Nova microversion 2.96 and 2.98

Nova 2.96 and 2.98 microversions change the response schema for
update server also but we missed to add the schema change for
update server APIs. Adding test for update server for both
microversion.

Also, 2.96 microversion adds new field 'pinned_availability_zone'
as mandatory in response, adding same in tempest schema.

Change-Id: I4d0fcca3224e65fdc92e60eb88c8850c5de795e7
3 files changed