Automatic merge from submit-queue
Fix Reaper timeout bug
This PR is an fix to the issue [noticed](https://github.com/kubernetes/kubernetes/pull/46468#discussion_r118589512) in a previous PR.
Previous behavior was to calculate a timeout but then ignore it, using `reaper.timeout` instead.
New behavior is to use the calculated timeout for `waitForStatefulSet`, which is passed to the Scaler.
Thanks to @foxish and @apelisse for pointing me in the right direction.
**Release note**:
```release-note
NONE
```
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