mod_sasl2_fast: Fix malformed-request when using HT-*-NONE (thanks lnj!) This crept into the previous commit which tried to fail early when CB was requested but unavailable - that commit did not actually check that CB *was* requested.

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summary: Log a message once per minute
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This module sends `-- MARK --` to the log once per minute. This may be
useful to give a sense of how busy the server is or see that logging and
timers are still working.