Network proxy: "Apply system wide" button dissapeared

[Fernando Sclavo]

In network proxy configuration screen, the "Apply system wide" button disappeared, so I can't change my proxy settings anymore.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: unity-control-center 15.04.0+16.04.20160413-0ubuntu3
ProcVersionSignature: Ubuntu 4.4.0-24.43-generic 4.4.10
Uname: Linux 4.4.0-24-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
CurrentDesktop: Unity
Date: Mon Jun 27 17:16:08 2016
EcryptfsInUse: Yes
ExecutablePath: /usr/bin/unity-control-center
InstallationDate: Installed on 2016-04-01 (86 days ago)
InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
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.
SourcePackage: unity-control-center
UpgradeStatus: Upgraded to xenial on 2016-04-22 (66 days ago)