Freeze break: gnome-shell: duplicate network connections

[Owen Taylor <otaylor redhat com>]

https://bugzilla.gnome.org/show_bug.cgi?id=645702

Under some circumstances network connections get added to the
network menu multiple times. This was because of a wrong parameter
being passed to a function so the code thought that the connection
wasn't in the menu and needed to be added gain.

Patch is simple and fairly obviously correct. I tested with normal
operation, though I wasn't able to reproduce the original bug on
demand. (I've seen it previously.)

- Owen