Remove os.Umask from overlay.BuildOverlayIndir

Adds tests to ensure that the overlay image contains the correct permissions.

Signed-off-by: Jonathon Anderson <janderson@ciq.com>

internal/pkg/util/cpio.go

@@ -1,31 +0,0 @@
-package util
-
-import (
-	"io"
-	"os"
-
-	"github.com/sassoftware/go-rpmutils/cpio"
-)
-
-/*
-Opens cpio archive and returns the file list
-*/
-func CpioFiles(name string) (files []string, err error) {
-	f, err := os.Open(name)
-	if err != nil {
-		return files, err
-	}
-	defer f.Close()
-
-	reader := cpio.NewReader(f)
-	for {
-		header, err := reader.Next()
-		if err == io.EOF {
-			return files, nil
-		}
-		if err != nil {
-			return files, err
-		}
-		files = append(files, header.Filename())
-	}
-}