used parent script PID for logger calls (sonic-net#19219)

[arp_update]: Use parent script PID for logger calls

Signed-off-by: Lawrence Lee <lawlee@microsoft.com>

files/scripts/arp_update

@@ -11,7 +11,7 @@ ARP_UPDATE_VARS_FILE="/usr/share/sonic/templates/arp_update_vars.j2"
 
 # Overload `logger` command to include arp_update tag
 logger () {
-    command logger -t "arp_update" "$@"
+    command logger -i "$$" -t "arp_update" "$@"
 }
 
 while /bin/true; do