[arp_update] Resolve neighbors from config_db (sonic-net#15006)

* To resolve NEIGH table entries present in CONFIG_DB. Without this change arp/ndp entries which we wish to resolve, and configured via CONFIG_DB are not resolved.

files/scripts/arp_update

@@ -124,8 +124,12 @@ while /bin/true; do
 
   # refresh neighbor entries from APP_DB in case of mismatch with kernel
   DBNEIGH=$(sonic-db-cli APPL_DB keys NEIGH_TABLE*)
-  KERNEIGH4=$(ip -4 neigh show | grep Vlan | cut -d ' ' -f 1,3  --output-delimiter=',')
-  KERNEIGH6=$(ip -6 neigh show | grep -v fe80 | grep Vlan | cut -d ' ' -f 1,3  --output-delimiter=',')
+
+  # resolve neighbor entries from CONFIG_DB in case of mismatch with kernel
+  DBNEIGH="$DBNEIGH $(sonic-db-cli CONFIG_DB keys NEIGH* | sed -e 's/|/:/g')"
+
+  KERNEIGH4=$(ip -4 neigh show | grep Vlan | grep -v 'FAILED\|INCOMPLETE' | cut -d ' ' -f 1,3  --output-delimiter=',')
+  KERNEIGH6=$(ip -6 neigh show | grep -v fe80 | grep Vlan | grep -v 'FAILED\|INCOMPLETE' | cut -d ' ' -f 1,3  --output-delimiter=',')
   for neigh in $DBNEIGH; do
       intf="$( cut -d ':' -f 2 <<< "$neigh" )"
       ip="$( cut -d ':' -f 3- <<< "$neigh" )"