Move resolveSymbolicLink to OS package and stub out for tests

Signed-off-by: Ian Campbell <ijc@docker.com>

pkg/server/helpers.go

@@ -297,19 +297,6 @@ func (c *criContainerdService) ensureImageExists(ctx context.Context, ref string
 	return &newImage, nil
 }
 
-// resolveSymbolicLink resolves a possbile symlink path. If the path is a symlink, returns resolved
-// path; if not, returns the original path.
-func resolveSymbolicLink(path string) (string, error) {
-	info, err := os.Lstat(path)
-	if err != nil {
-		return "", err
-	}
-	if info.Mode()&os.ModeSymlink != os.ModeSymlink {
-		return path, nil
-	}
-	return filepath.EvalSymlinks(path)
-}
-
 // loadCgroup loads the cgroup associated with path if it exists and moves the current process into the cgroup. If the cgroup
 // is not created it is created and returned.
 func loadCgroup(cgroupPath string) (cgroups.Cgroup, error) {