Only clean up containerd hosts dirs managed by k3s

[brandond]

Proposed Changes

Only clean up containerd hosts dirs managed by k3s

If the user creates their own hosts.toml, or drops CA or client certs in the directory by hand, we shouldn't delete them whenever K3s starts.

Types of Changes

enhancement

Verification

1. Create your own host dir at /var/lib/rancher/k3s/agent/etc/containerd/certs.d/MYREGISTRY and add custom hosts.toml and/or certs. Restart K3s, and note that the custom content you created is left alone.
2. Add an entry for MYREGISTRY in registries.yaml and restart k3s, note that the custom files are cleaned up and replaced with the K3s-managed hosts.toml
3. Edit the file at /var/lib/rancher/k3s/agent/etc/containerd/certs.d/MYREGISTRY/hosts.toml to remove the DO NOT EDIT header and restart k3s; note that it is reverted to the managed content.
4. Remove MYREGISTRY from registries.yaml and restart k3s. Note that /var/lib/rancher/k3s/agent/etc/containerd/certs.d/MYREGISTRY is removed.

Testing

Linked Issues

• Custom agent/etc/containerd/certs.d/* files are deleted by k3s on startup #10787

User-Facing Change

Further Comments

[codecov]

Codecov Report

Attention: Patch coverage is 12.00000% with 22 lines in your changes missing coverage. Please review.

Project coverage is 44.12%. Comparing base (28ceeec) to head (727d8a5).
Report is 8 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/agent/containerd/config.go	12.00%	18 Missing and 4 partials ⚠️

❗ There is a different number of reports uploaded between BASE (28ceeec) and HEAD (727d8a5). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (28ceeec)	HEAD (727d8a5)
e2etests	7	6

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #10823      +/-   ##
==========================================
- Coverage   49.98%   44.12%   -5.87%     
==========================================
  Files         178      178              
  Lines       14753    14777      +24     
==========================================
- Hits         7375     6521     -854     
- Misses       6039     7060    +1021     
+ Partials     1339     1196     -143     

Flag	Coverage Δ
e2etests	36.47% <12.00%> (-9.71%)	⬇️
inttests	36.77% <12.00%> (-0.01%)	⬇️
unittests	13.57% <0.00%> (-0.03%)	⬇️

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