Heat autoscaling scenario test

This test starts with a single server and scales up to
three servers triggered by a script that consumes memory.

Seven minutes after stack creation, memory consumption script
will quit and the scale down alarms will scale back down to
a single server.

Due to the nature of this test, it takes about 10 minutes to
run locally.

The scenario test has been put in package orchestration
for the following reasons:
- this will be the first of many heat scenario tests
- this will allow a tox filter to run this test for the
  slow heat gating job

Change-Id: I53ed12369d12b902108b9b8fa7885df34f6ab51f
Merge "Heat autoscaling scenario test"