extra-packages: Add krb5-libs
    
    The krb5-libs package was added to the base toolbox images to ensure
    the presence of the /etc/krb5.conf.d directory with the correct
    permissions. Currently, the package is already pulled in by various
    dependencies. Therefore, it doesn't increase the size of the base
    image, but serves as a safeguard against any inadvertent changes.
    
    https://github.com/debarshiray/toolbox/pull/74