[dovecot/core] e052c2: auth: Disable auth caching for passwd-file

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/dovecot/core
  Commit: e052c2247f6febbe559a593948ed8ef9f2118435
      https://github.com/dovecot/core/commit/e052c2247f6febbe559a593948ed8ef9f2118435
  Author: Timo Sirainen <timo.sirainen at dovecot.fi>
  Date:   2016-03-29 (Tue, 29 Mar 2016)

  Changed paths:
    M src/auth/passdb-passwd-file.c
    M src/auth/userdb-passwd-file.c

  Log Message:
  -----------
  auth: Disable auth caching for passwd-file

Its caching is usually unnecessary, because the passwd-files are efficiently
in memory already. It's also problematic, because extra_fields can contain
%variables, which can be lookup-dependent. So for example if %{lport} is used
in extra_fields, it would need to be included in the cache key. But because
different variables can be used by different users' extra_fields, there's
really no good way to include all of it in the cache key.