VPN authentication steals focus on login screen.

[mark johnson]

Steps to reproduce:
Set up a VPN connection in network manager using password authentication, and store the password.
Set up a Wireless network to connect automaticall, and to automatically connect to the configured VPN.
Confirm that the network and VPN connect without prompting you for the password.
Log out or reboot to the login screen.
Wait for the wireless network to connect. The VPN authentication dialog appears, and prevents you from typing in the login form. The dialogue can be cancelled, but it reappears shortly after, making it difficult to log in.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: network-manager 1.1.93-0ubuntu4
ProcVersionSignature: Ubuntu 4.4.0-22.40-generic 4.4.8
Uname: Linux 4.4.0-22-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
CurrentDesktop: Unity
Date: Sun May 29 20:38:50 2016
EcryptfsInUse: Yes
IfupdownConfig:
 # interfaces(5) file used by ifup(8) and ifdown(8)
 auto lo
 iface lo inet loopback
InstallationDate: Installed on 2015-08-31 (272 days ago)
InstallationMedia: Ubuntu 14.04.3 LTS "Trusty Tahr" - Beta amd64 (20150805)
NetworkManager.state:
 [main]
 NetworkingEnabled=true
 WirelessEnabled=true
 WWANEnabled=true
 WimaxEnabled=true
SourcePackage: network-manager
UpgradeStatus: Upgraded to xenial on 2016-04-22 (36 days ago)
mtime.conffile..etc.NetworkManager.NetworkManager.conf: 2015-09-02T20:13:30.618545
nmcli-dev:
 DEVICE TYPE STATE DBUS-PATH CONNECTION CON-UUID CON-PATH
 tun0 tun connected /org/freedesktop/NetworkManager/Devices/2 tun0 1d00cd2d-9244-4385-a7b6-0272cd616049 /org/freedesktop/NetworkManager/ActiveConnection/10
 wlan0 wifi connected /org/freedesktop/NetworkManager/Devices/0 MJ_JF bfecb4ab-406c-4cd1-bcdf-913b4973f119 /org/freedesktop/NetworkManager/ActiveConnection/8
 lo loopback unmanaged /org/freedesktop/NetworkManager/Devices/1 -- -- --
nmcli-nm: Error: command ['nmcli', '-f', 'all', 'nm'] failed with exit code 2: Error: Object 'nm' is unknown, try 'nmcli help'.