screen brightness is not undimmed when user becomes active again

[Robert Nürnberg]

Since upgrading to kubuntu 16.04, the screen brightness remains low (dimmed) after a period of inactivity even when the user becomes active again. Laptop is on AC power throughout.

Steps to reproduce:
 * in system settings->energy saving set dim period to 5 min
 * after 10 min screen is dimmed
 * when moving mouse and after possibly unlocking screen, the screen brightness remains low

Expect to happen: screen brightness goes back up

Workaround: When screen brightness stays too low, go to system settings->energy saving, select
box "Screen brightness", select any Level of brightness different from current value, and click Apply.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: systemsettings 4:5.5.5-0ubuntu1
ProcVersionSignature: Ubuntu 4.4.0-36.55-generic 4.4.16
Uname: Linux 4.4.0-36-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
CurrentDesktop: KDE
Date: Tue Sep 13 09:57:52 2016
ExecutablePath: /usr/bin/systemsettings5
InstallationDate: Installed on 2014-08-05 (769 days ago)
InstallationMedia: Ubuntu 14.04.1 LTS "Trusty Tahr" - Release amd64 (20140722.2)
JournalErrors:
 Error: command ['journalctl', '-b', '--priority=warning', '--lines=1000'] failed with exit code 1: Hint: You are currently not seeing messages from other users and the system.
       Users in the 'systemd-journal' group can see all messages. Pass -q to
       turn off this notice.
 No journal files were opened due to insufficient permissions.
ProcEnviron:
 LANGUAGE=en_GB:en
 PATH=(custom, user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_GB.iso88591
 SHELL=/bin/tcsh
SourcePackage: systemsettings
UpgradeStatus: Upgraded to xenial on 2016-08-01 (42 days ago)