refactor: some kubeadm init phase constants

[calvin0327]

What type of PR is this?

/kind feature
/kind cleanup

What this PR does / why we need it:

There are some values that need constants

Special notes for your reviewer:

Please correct me if the modification is incorrect

Does this PR introduce a user-facing change?

NONE

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[calvin0327]

/retest

[neolit123]

thanks

/lgtm
/approve
/triage accepted
/priority backlog

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: calvin0327, neolit123

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/retest