nasty error messages about SQL and auxpropfunc

[IMAP List Administration]

Hello Folks,

I'm in the process of moving my mail server from:

    cyrus-imapd-2.4.17p8
    cyrus-sasl-2.1.26p11

to:
    cyrus-imapd-2.5.7
    cyrus-sasl-2.1.26p15

My server uses /etc/sasldb2.db for authentication.

In my /etc/imapd.conf file I have:
    sasl_pwcheck_method: auxprop
    sasl_mech_list: CRAM-MD5 DIGEST-MD5

Upon starting the new imapd server, things seem to work, but I noticed two error
messages I have not seen before which spam up my syslog:
    imapd/imaps[15690]: SQL engine 'mysql' not supported
    imapd/imaps[15690]: auxpropfunc error no mechanism available

I tried adding this to /etc/imapd.conf, in vain:
    sasl_auxprop_plugin: sasldb

I've spent a fair amount of time reading the imapd and sasl documentation.
Google turns up similar complaints, some with "fixes". As far as I can tell, all
the proposals for "fixing" the problem are the same: remove the sasl sql library.

I did this and behold, the messages disappeared.

To me this belongs in the smelly and dirty hack category. There *must* be a way
to tell sasl not to use some plugin.

Could someone please give me a hint how to do this?

thanks,
rob