Allowes multiple instance of update-manager

[Imri Paloja]

When clicking the update-manager icon multiple times, it opens multiple instance of the update-manager.

This should not happen. Only one instance should be allowed!

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: update-manager 1:0.186
ProcVersionSignature: Ubuntu 3.8.0-25.37-generic 3.8.13
Uname: Linux 3.8.0-25-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.9.2-0ubuntu8.1
Architecture: amd64
Date: Sat Jun 29 00:34:27 2013
GsettingsChanges:
 b'com.ubuntu.update-manager' b'first-run' b'false'
 b'com.ubuntu.update-manager' b'launch-time' b'1372458815'
 b'com.ubuntu.update-manager' b'show-details' b'true'
 b'com.ubuntu.update-manager' b'window-height' b'618'
 b'com.ubuntu.update-manager' b'window-width' b'565'
InstallationDate: Installed on 2013-05-18 (41 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Release amd64 (20130424)
MarkForUpload: True
PackageArchitecture: all
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=nl_NL.UTF-8
 SHELL=/bin/bash
SourcePackage: update-manager
UpgradeStatus: No upgrade log present (probably fresh install)