edx autoscaling groups

[Ardiea]

Revisit the Autoscaling for edx. Previously, when autoscaling was configured, edx would go into a death sprial of up/down/up/down over and over. Still need autoscaling but it needs to be smarter than the previous implementation.

Sar has load testing code somewhere that we can use to give this a nudge and hopefully trigger the autoscaling.