Unable to make use of least-nodes expander in the autoscaler

[Kaikj]

Which component are you using?: Cluster Autoscaler

What version of the component are you using?: The bug exists in the master branch

Component version:

What k8s version are you using (kubectl version)?: The version of kubectl does not matter

kubectl version Output

$ kubectl version

What environment is this in?:
This affects all environments as the bug is in the code

What did you expect to happen?:
The least-nodes expander to be selected after choosing it

What happened instead?:
The least-nodes expander is not part of the set of available expanders

How to reproduce it (as minimally and precisely as possible):
Simply try to make use of least-nodes expander.

The least nodes expander introduced in #6792 did not add the expander into the list of Available Expanders. The easy fix would be to simply add it in but I cannot be sure if it is intended to be left out for now or if it has just been missed out.

Happy to open a PR for this if it helps. The bug occurs in https://github.com/kubernetes/autoscaler/blob/master/cluster-autoscaler/expander/expander.go

Anything else we need to know?:

[adrianmoisey]

/area cluster-autoscaler

[areeba-anwar]

Environment: This issue affects all environments since the bug exists within the code itself.

Expected Behavior: After selecting the least-nodes expander, it should be available as an option.

Actual Behavior: The least-nodes expander is missing from the list of available expanders.

Steps to Reproduce:

Attempt to use the least-nodes expander.
Observe that it does not appear in the set of available expanders.