[Feature] ch18968 singlenode k8s support 1.21

[kentwelcome]

Signed-off-by: Kent Huang kentwelcome@gmail.com

PR checklist

• [x] Ensure you have added or ran the appropriate tests for your PR.
• [x] DCO signed

What type of PR is this? Feature

What this PR does / why we need it: Single node microk8s support 1.21

Which issue(s) this PR fixes: ch18968

Special notes for your reviewer:

Does this PR introduce a user-facing change?: