BUG Fix: add sudo to run command arping

Set 'PUBLIC_INTERFACE' in local.conf, so the code will
be entered into _move_neutron_addresses_route of
neutron-legacy.

But if lack of sudo to run command arping, the information
"arping: socket: Operation not permitted" occurs. So add
'sudo' for 'ARP_CMD' of lib/neutron-legacy.

Change-Id: I8ac8a9bc2bbba049c45b28bf9b93d9a10e398fe6
Closes-Bug: #1783046

Author: zhubx007

lib/neutron-legacy

@@ -633,7 +633,7 @@ function _move_neutron_addresses_route {
             IP_UP="sudo ip link set $to_intf up"
             if [[ "$af" == "inet" ]]; then
                 IP=$(echo $IP_BRD | awk '{ print $1; exit }' | grep -o -E '(.*)/' | cut -d "/" -f1)
-                ARP_CMD="arping -A -c 3 -w 4.5 -I $to_intf $IP "
+                ARP_CMD="sudo arping -A -c 3 -w 4.5 -I $to_intf $IP "
             fi
         fi