ipa-server-install: handle error when calling kdb5_util create
    
    ipa-server-install creates the kerberos container by calling
    kdb5_util create -s -r $REALM -x ipa-setup-override-restrictions
    
    but does not react on failure of this command. The installer fails later
    when trying to create a ldap principal, and it is difficult to diagnose the
    root cause.
    
    The fix raises a RuntimeException when kdb5_util fails, to make sure
    that the installer exits immediately with a proper error message.
    
    Note: no test added because there is no easy reproducer. One would need to
    stop dirsrv just before calling kdb5_util to simulate a failure.
    
    https://pagure.io/freeipa/issue/7438
    
    Reviewed-By: Robbie Harwood <rharwood@redhat.com>