docs: recommend SCRAM-SHA-256 SASL mech instead of SHA-1 variant

The SHA-256 variant better meats modern security expectations.
Also warn that the password file is storing entries in clear
text.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
2 files changed