ignore ENOENT errors when parsing registries.d files

As always listing files in a dir to then read them is racy as the file
might have been removed in the meantime. Thus we must ignore ENOENT
errors when the file is opened.

This is not just a theoretical problem, the reason I am here is because
it caused a flake in the podman CI[1]:
... open /etc/containers/registries.d/podman-test-only-temporary-addition.yaml: no such file or directory

[1] https://api.cirrus-ci.com/v1/artifact/task/6673405799301120/html/int-podman-fedora-40-root-host-boltdb.log.html#t--Podman-push-podman-push-to-local-registry-with-authorization--1

Signed-off-by: Paul Holzinger <[email protected]>

docker/registries_d.go

@@ -3,6 +3,7 @@ package docker
 import (
 	"errors"
 	"fmt"
+	"io/fs"
 	"net/url"
 	"os"
 	"path"
@@ -129,6 +130,11 @@ func loadAndMergeConfig(dirPath string) (*registryConfiguration, error) {
 		configPath := filepath.Join(dirPath, configName)
 		configBytes, err := os.ReadFile(configPath)
 		if err != nil {
+			if errors.Is(err, fs.ErrNotExist) {
+				// file must have been removed between the directory listing
+				// and the open call, ignore that as it is a expected race
+				continue
+			}
 			return nil, err
 		}