We currently only have the option '-k' which forces the usage of kerberos.
smbtorture pretents to support '-k', '-k yes' and '-k no', I'll have to check
if that works correct, otherwise we may introduce --use-kerberos=yes|no.
'--option=gensec:gse_krb5=no' would also work in the current code.
This is fixed in 4.15