netifd: fix an error message during network shutdown

netifd: fix an error message during network shutdown

When 'wifi down' is called by /etc/init.d/network, it is run from
stop_service( ). This function is in turn invoked from stop( ).
stop( ) messes up the order by first procd_kill-ing the network
settings, then calling wifi to down the wifi networking
interfaces. By redefining stop( ) instead, the proper order is
restored.

Signed-off-by: Michel Stam <m.stam@fugro.nl>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@42745 3c298f89-4303-0410-b956-a3cf2f4a3e73