[Release-1.28] - Fix remaining corner cases in containerd certs.d support

[brandond]

Backport fix for Fix remaining corner cases in containerd certs.d support

• Fix remaining corner cases in containerd certs.d support #9341

[ShylajaDevadiga]

Validated using k3s version v1.28.8-rc1+k3s1

Environment Details

Infrastructure
Cloud EC2 instance

Node(s) CPU architecture, OS, and Version:
Ubuntu 22.04

$ cat /etc/rancher/k3s/registries.yaml 
---
mirrors:
  docker.io:
    endpoint:
      - https://registry.example.com
      - docker.io
  k8s.gcr.io:
    endpoint:
      - https://registry.example.com
      - k8s.gcr.io
configs:
  registry.example.com:
    auth:
      username: testusername
      password: testpassword
    tls:
      ca_file: /home/ubuntu/ca.pem

Steps to validate

1. Configure private registry
2. Create the registries.yaml with the last registry in the endpoint list as the default to /etc/rancher/k3s
3. Install k3s.
4. Validate certs.d//hosts.toml is generated

Results from reproducing the issue:

$ k3s -v
k3s version v1.28.7+k3s1 (051b14b2)
go version go1.21.7

$ sudo cat  /var/lib/rancher/k3s/agent/etc/containerd/certs.d/docker.io/hosts.toml
cat: /var/lib/rancher/k3s/agent/etc/containerd/certs.d/docker.io/hosts.toml: No such file or directory

Results from validating the issue:

$ k3s -v
k3s version v1.28.8-rc1+k3s1 (653dd61a)
go version go1.21.8

$ sudo cat  /var/lib/rancher/k3s/agent/etc/containerd/certs.d/k8s.gcr.io/hosts.toml
# File generated by k3s. DO NOT EDIT.

server = "https://k8s.gcr.io/v2"
capabilities = ["pull", "resolve", "push"]



[host."https://registry.example.com/v2"]
  capabilities = ["pull", "resolve"]
  ca = ["/home/ubuntu/ca.pem"]

$ sudo cat  /var/lib/rancher/k3s/agent/etc/containerd/certs.d/docker.io/hosts.toml
# File generated by k3s. DO NOT EDIT.

server = "https://registry-1.docker.io/v2"
capabilities = ["pull", "resolve", "push"]



[host."https://registry.example.com/v2"]
  capabilities = ["pull", "resolve"]
  ca = ["/home/ubuntu/ca.pem"]