Add parametrization default_schedule_zone config option in salt-formula-nova

The default_schedule_zone is a nova config option that defines an AZ
that would beset by nova API if a user doesn't provide
--availability-zone flag when booting an instance.
So now we can override it if necessary.

Related User Story: PROD-17268
Change-Id: Ic35156d1d9671045e5a04c7c5a8011c5d2c98d68
6 files changed