Remove reference to the turned off test 'test_autoscaling'

Platform heat test 'test_autoscaling' was turned off, so need to remove all
references to this test in system tests.

Change-Id: Ifa45a9bcc20608cfe016f328886c4f363c612b9e
Related-Bug: #1334346
Merge "Remove reference to the turned off test 'test_autoscaling'" into stable/5.0