Make instance_action_events.traceback a non-required field

instance_action_events.traceback can only be seen by admin users
with default policy.json,
"os_compute_api:os-instance-actions:events":
    "rule:admin_api or role:InstanceEvents"
so it should not be deemd as a required field in schema.
https://developer.openstack.org/api-ref/compute/#show-server-action-details

Change-Id: Id85c75347eba2b10b8ecc0ea262fd870281c610d
Closes-Bug: #1783275
1 file changed