package/dovecot: add upstream security fix for CVE-2022-30550

An issue was discovered in the auth component in Dovecot 2.2 and 2.3 before
2.3.20.  When two passdb configuration entries exist with the same driver
and args settings, incorrect username_filter and mechanism settings can be
applied to passdb definitions.  These incorrectly applied settings can lead
to an unintended security configuration and can permit privilege escalation
in certain configurations.  The documentation does not advise against the
use of passdb definitions that have the same driver and args settings.  One
such configuration would be where an administrator wishes to use the same
PAM configuration or passwd file for both normal and master users but use
the username_filter setting to restrict which of the users is able to be a
master user.

https://dovecot.org/pipermail/dovecot-news/2022-July/000477.html



Signed-off-by: Peter Korsgaard <peter@korsgaard.com>