Add pki_pin only when needed
    
    If both the pki-tomcat NSS database and its password.conf have been
    created, don't try to override the password.conf file.
    
    https://pagure.io/freeipa/issue/6839
    
    Reviewed-By: Tomas Krizek <tkrizek@redhat.com>
    Reviewed-By: Christian Heimes <cheimes@redhat.com>