feat: ability to set the status configMap name

[trutx]

This ports kubernetes#3888 into the v1.17.4 release

Also porting kubernetes#3630 so two cluster-autoscaler instances don't collide in leader election context.

[trutx]

Also porting this PR kubernetes#3940 to avoid what's below to happen on redeploys/pod restarts:

I0316 11:59:20.270592       1 main.go:371] Cluster Autoscaler 1.17.4
I0316 11:59:20.319842       1 leaderelection.go:242] attempting to acquire leader lease  kube-system/cluster-autoscaler...
I0316 11:59:20.325219       1 leaderelection.go:352] lock is held by cluster-autoscaler-7655f578d-6x9b2 and has not yet expired
I0316 11:59:20.325239       1 leaderelection.go:247] failed to acquire lease kube-system/cluster-autoscaler
I0316 11:59:23.781962       1 leaderelection.go:352] lock is held by cluster-autoscaler-7655f578d-6x9b2 and has not yet expired
I0316 11:59:23.781977       1 leaderelection.go:247] failed to acquire lease kube-system/cluster-autoscaler
I0316 11:59:28.044788       1 leaderelection.go:352] lock is held by cluster-autoscaler-7655f578d-6x9b2 and has not yet expired
I0316 11:59:28.044803       1 leaderelection.go:247] failed to acquire lease kube-system/cluster-autoscaler
I0316 11:59:31.645043       1 leaderelection.go:352] lock is held by cluster-autoscaler-7655f578d-6x9b2 and has not yet expired
I0316 11:59:31.645059       1 leaderelection.go:247] failed to acquire lease kube-system/cluster-autoscaler
I0316 11:59:34.700998       1 leaderelection.go:352] lock is held by cluster-autoscaler-7655f578d-6x9b2 and has not yet expired
I0316 11:59:34.701012       1 leaderelection.go:247] failed to acquire lease kube-system/cluster-autoscaler
I0316 11:59:37.742850       1 leaderelection.go:252] successfully acquired lease kube-system/cluster-autoscaler

[idleyoungman]

Minor nit, doesn't need to block moving ahead: looks like the const for StatusConfigMapName is still there in cluster-autoscaler/clusterstate/utils/status.go but was removed in the

[idleyoungman]

LGTM w/ the note about the unused const.

[trutx]

Good catch @idleyoungman, totally missed that one. Fixed.