[chassis-packet] fix the issue of internal ip arp not getting resolve…

…d. (#12127)

Fix the issue where arp_update will not ping some of the ip's even
though they are in failed state since grep of that ip on ip neigh show
command does not do exact word match and can return multiple match.

files/scripts/arp_update

@@ -22,10 +22,10 @@ while /bin/true; do
       fi
       for nexthop in $STATIC_ROUTE_NEXTHOPS; do
           if [[ $nexthop == *"."* ]]; then
-              neigh_state=( $(ip -4 neigh show | grep $nexthop | tr -s ' ' | cut -d ' ' -f 3,4) )
+              neigh_state=( $(ip -4 neigh show | grep -w $nexthop | tr -s ' ' | cut -d ' ' -f 3,4) )
               ping_prefix=ping
           elif [[ $nexthop == *":"* ]] ; then
-              neigh_state=( $(ip -6 neigh show | grep $nexthop | tr -s ' ' | cut -d ' ' -f 3,4) )
+              neigh_state=( $(ip -6 neigh show | grep -w $nexthop | tr -s ' ' | cut -d ' ' -f 3,4) )
               ping_prefix=ping6
           fi