[dovecot/core] d81702: quota: Improve error messages

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/dovecot/core
  Commit: d81702ddd148abde32cbe2a45f6239e1baee6907
      https://github.com/dovecot/core/commit/d81702ddd148abde32cbe2a45f6239e1baee6907
  Author: Timo Sirainen <timo.sirainen at dovecot.fi>
  Date:   2017-10-28 (Sat, 28 Oct 2017)

  Changed paths:
    M src/plugins/quota/quota-storage.c
    M src/plugins/quota/quota.c

  Log Message:
  -----------
  quota: Improve error messages