Add test for scaling up a function

[ivanayov]

Use /system/scale-function for scaling .

Test cases:
1x without limits
1x with limits
1x autoscaling disabled
1x 0 to 1 replicas

[ivanayov]

Derek assign: me

[alexellis]

Let's do the first PR where we scale using the manual endpoint then check the API for how many replicas we expected. Once that's merged, we can look at the next scenario to cover.

[ivanayov]

@alexellis I'm now on the TODO list from #14

[ivanayov]

After re-running the test several times, I consider random behaviour regarding labels and number of replicas created. Working to fix it.

[ivanayov]

Scaling limit restrictions are ignored when calling /system/scale-function.
Tested manually separately from the test. I'm going to remove the labels from the code for now and we can consider this as an separate issue.