cli: fix deactivation for multiple connections (bgo #740775) (rh #1168383)

$ nmcli connection down aa bb cc

It has been broken by commit 20566c76de0d18162af020852ae1e2055addcfff.

Fixups by dcbw.

https://bugzilla.gnome.org/show_bug.cgi?id=740775
https://bugzilla.redhat.com/show_bug.cgi?id=1168383