net: make lookup of iproute2 dynamic

The iproute2, macvlan and vlan modules had several possible hard coded
paths for the iproute2 binary. Now we look for it in the path.

net/macvlan.sh

@@ -3,18 +3,12 @@
 # Copyright (c) 2007-2008 Roy Marples <roy@marples.name>
 # All rights reserved. Released under the 2-clause BSD license.
 
-_ip()
-{
-	if [ -x /bin/ip ]; then
-		echo /bin/ip
-	else
-		echo /sbin/ip
-	fi
-}
-
 macvlan_depend()
 {
-	program $(_ip)
+	local x
+	x=$(_which ip)
+	[ -z "${X}" ] && return 1
+	program $x
 	after interface
 	before dhcp macchanger
 }