Automatic merge from submit-queue (batch tested with PRs 65648, 65700, 64976, 65692, 65667). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
kubeadm: Replace GetCoreImage with less error prone functions
**What this PR does / why we need it**:
GetCoreImage is a too generic function, that takes too many arguments. This
makes it prone to errors that may be difficult to trace. The solution is to
split it into the following couple of functions with a more targeted interface:
- GetKubeControlPlaneImage used to fetch Kubernetes control plane images or the
unified control plane image (if one is specified).
- GetEtcdImage is used to fetch the etcd image.
In addition to these, a couple of new utility functions are also created:
- GetKubeControlPlaneImageNoOverride used like GetKubeControlPlaneImage but
does not return the unified control plane image (even if it is set).
- GetGenericArchImage returns image path in the form of "prefix/image-goarch:tag"
Signed-off-by: Rostislav M. Georgiev <rostislavg@vmware.com>
**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixeskubernetes/kubeadm#800
**Special notes for your reviewer**:
/cc @kubernetes/sig-cluster-lifecycle-pr-reviews
/area kubeadm
/assign @luxas
/assign @timothysc
/cc @chuckha
/kind enhancement
**Release note**:
```release-note
NONE
```
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