Smartd doesn't run other scripts after 10mail

When I put any scripts under `/etc/smartmontools/run.d`, they're not executed.
This is valid also for the package `smart-notifier`, which in fact, doesn't show anything on my system.

To reproduce:

- activate smartd test mode: `perl -i -pe 's/^(DEVICESCAN.*)/$1 -M test/' /etc/smartd.conf`
- either install `smart-notifier`, or write any other simple script
- reboot and logon
- `smart-notifier` (or the simple script) won't have any effect; `sudo mail` will show though, that a warning message has been sent.

This is caused by `/usr/share/smartmontools/smartd-runner`, but I don't know how `run-parts` works exactly.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: smartmontools 6.4+svn4214-1 [modified: var/lib/smartmontools/drivedb/drivedb.h]
Uname: Linux 4.12.10-041210-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.10
Architecture: amd64
CurrentDesktop: XFCE
Date: Sun Sep 3 17:52:38 2017
EcryptfsInUse: Yes
InstallationDate: Installed on 2017-02-25 (190 days ago)
InstallationMedia: Xubuntu 16.04.2 LTS "Xenial Xerus" - Release amd64 (20170215)
SourcePackage: smartmontools
UpgradeStatus: No upgrade log present (probably fresh install)
mtime.conffile..etc.smartd.conf: 2017-09-03T17:11:17.135646