Investigate Why Preview Is Scaling Up To 10x Minimum

[JamieB-gu]

Since adding scaling alarms to Preview on the 1st of August, to allow it to scale, we've seen spikes in scaling up to ten times the minimum capacity. For example, the minimum is 3 boxes, and we've seen scaling take it up to ~29 boxes.

This is a problem, because the max capacity is also only 10x the minimum, i.e. 30 boxes. If a deploy runs while we're scaled up this much, it fails, because the deploy needs to double the boxes but it doesn't have the headroom.