Automatic merge from submit-queue (batch tested with PRs 62455, 62465, 62427, 62416, 62411). 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>.
Fix kubeadm upgrade ignores HighAvailability feature gate
**What this PR does / why we need it**:
This PR fixes https://github.com/kubernetes/kubeadm/issues/731
**Which issue(s) this PR fixes**:
Fixes https://github.com/kubernetes/kubeadm/issues/731
**Special notes for your reviewer**:
The problem is a regression introduced by [#55952](https://github.com/kubernetes/kubernetes/pull/55952) which added a --feature-gates
flag to `kubeadm upgrade`, to be used for updating feature gates during the upgrade process (so it is update + upgrade).
The original implementation always override the actual feature gates with the flag value, even when the flag is not set; this PR fixes this behaviour making `kubeadm upgrade` considers the flag value only if set, otherwise actual feature gates will be preserved.
/cc @kubernetes/sig-cluster-lifecycle-pr-reviews @kubernetes/sig-cluster-lifecycle-bugs
**Release note**:
```release-note
Fixed#731 kubeadm upgrade ignores HighAvailability feature gate
```
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