[dovecot/core] 904765: director: Fix logging disconnection error reasons

[GitHub]

  Branch: refs/heads/master-2.2
  Home:   https://github.com/dovecot/core
  Commit: 904765b05880927978c2f0aac7ba2b72e961cc32
      https://github.com/dovecot/core/commit/904765b05880927978c2f0aac7ba2b72e961cc32
  Author: Timo Sirainen <timo.sirainen at dovecot.fi>
  Date:   2017-11-28 (Tue, 28 Nov 2017)

  Changed paths:
    M src/director/director-connection.c

  Log Message:
  -----------
  director: Fix logging disconnection error reasons

The previous commit set errno=0, which weren't logged. If error string is
provided, it doesn't matter what the errno is set (as long as it's not 0),
so we'll just use EINVAL.