Auto-generate certs in-memory

[liggitt]

The dashboard is currently writing autogenerated cert files to a directory managed by the kubelet secret mounter.

At best, those files are auto-removed shortly after being written and the server startup races with the removal.

At worst, the location is mounted readonly and the dashboard fails to start.

There's no reason to write files to a location where they will just be cleaned up later (and doing so is breaking the dashboard when the location is read-only... see https://github.com/kubernetes/kubernetes/pull/58720/files#diff-7ab88bb7654d97946d6328f11f29d177)

This PR changes the dashboard to keep auto-generated certs in memory

[codecov]

Codecov Report

Merging #2795 into master will not change coverage.
The diff coverage is 0%.

@@           Coverage Diff           @@
##           master    #2795   +/-   ##
=======================================
  Coverage   54.17%   54.17%           
=======================================
  Files         564      564           
  Lines       12199    12199           
=======================================
  Hits         6609     6609           
  Misses       5334     5334           
  Partials      256      256

Impacted Files	Coverage Δ
src/app/backend/cert/ecdsa/creator.go	14.89% <0%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 2c7e17e...29535d3. Read the comment docs.

[floreks]

/lgtm
/approve

Thanks! This definitely helps, however we have bigger issue here. I thought that if we'd mount secret in RW mode then it would sync secret data in both ways. Since this is not the case then every replica will use different autogenerated certificates. We have to work on that and try to sync them across replicas somehow.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: floreks, liggitt

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these OWNERS Files:

• OWNERS [floreks]

You can indicate your approval by writing /approve in a comment
You can cancel your approval by writing /approve cancel in a comment