vm/network: replace route in more elegant way

network/vif-route-qubes

@@ -29,7 +29,7 @@ case "$command" in
 	online)
 		ifconfig ${vif} up
 		echo 1 >/proc/sys/net/ipv4/conf/${vif}/proxy_arp
-		ipcmd='add'
+		ipcmd='replace'
 		iptables_cmd='-I FORWARD 1'
 		cmdprefix=''
 		;;
@@ -45,7 +45,6 @@ if [ "${ip}" ] ; then
 	# If we've been given a list of IP addresses, then add routes from dom0 to
 	# the guest using those addresses.
 	for addr in ${ip} ; do
-		${cmdprefix} ip route del ${addr} || true
 		${cmdprefix} ip route ${ipcmd} ${addr} dev ${vif} || true
 	done
 		echo ${cmdprefix} iptables $iptables_cmd -i ${vif} \! -s ${ip} -j DROP