AS-274: DELETE groups/<groupId>/servers/<serverId> tests

Non-blocking - there doesn't seem to be a case that covers change=0 (which we disallow), but since 0 evaluates to `False`, this would prevent this method from being used for such a test.  That might be fine, but we could also change this to specifically only set it to `int(self.autoscale_config.sp_change)` if `sp_change is None`