In a terminal go
Code:
gksu gedit /var/lib/polkit-1/localauthority/10-vendor.d/com.ubuntu.desktop.pkla
For the first listed override change the ResultActive=yes to
ResultActive=auth_admin_keep
Or if you want to 'deactivate' all three included overrides then simply
Code:
sudo mv /var/lib/polkit-1/localauthority/10-vendor.d/com.ubuntu.desktop.pkla /var/lib/polkit-1/localauthority/10-vendor.d/com.ubuntu.desktop.pkla.bak
First option is probably the best