Revert "net/ifconfig net/iproute2: support lookup ifconfig/ip dynamically"

This reverts commit f583030e3c.

The previous commit did not account for the case of not having iproute2
installed.

Reported-by: Duncan <1i5t5.duncan@cox.net>
X-Gentoo-Bug: 397875
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=397875

net/iproute2.sh

@@ -6,7 +6,7 @@ _ip()
 	if [ -x /bin/ip ]; then
 		echo /bin/ip
 	else
-		which ip 2>/dev/null
+		echo /sbin/ip
 	fi
 }