connection-editor: fix wired 802-1x secrets saving

In case of wired 802-1x connection a temporary connection object is used,
but since NM commit 6a19e68a7d856629600655a076b0cea4be346799
secrets are cleared when the object is destroyed.
So duplicate 802-1x settings instead of using g_object_ref().

https://mail.gnome.org/archives/networkmanager-list/2016-May/msg00097.html