network: Don't unref device after when parsing arguments

When we add the NetDevice pointer to the GPtrArray, we have
a single reference owned by the panel. When iterating over
this GPtrArray, no reference is taken.

The problem is that the code to handle command-line arguments
was unreferencing the NetDevices when iterating over it,
creating a disparity in the ref/unref pairs.

Fix that by simply not unreferencing the NetDevice instance
when iterating over it.

https://bugzilla.gnome.org/show_bug.cgi?id=786514

panels/network/cc-network-panel.c

@@ -376,8 +376,6 @@ handle_argv (CcNetworkPanel *panel)
                         g_object_unref (connection);
                 }
 
-                g_object_unref (object_tmp);
-
                 if (done)
                         return;
         }