[dovecot/core] bf277f: lib-storage: reintroduce mail_index_set_fsync_mode

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/dovecot/core
  Commit: bf277f94101249133349c0560dad0463c821a2ef
      https://github.com/dovecot/core/commit/bf277f94101249133349c0560dad0463c821a2ef
  Author: Fabian Freyer <fabian.freyer at physik.tu-berlin.de>
  Date:   2018-04-06 (Fri, 06 Apr 2018)

  Changed paths:
    M src/lib-storage/index/index-storage.c

  Log Message:
  -----------
  lib-storage: reintroduce mail_index_set_fsync_mode

This patch fixes a regression introduced in
638600575ee95f2513c683ef09cb188f76eacd22 where mail_fsync=always would
not be honoured, leading to fatal "nfs flush requires mail_fsync=always"
errors.