dhcp ntp: fix logic of ntp server override

Author: themactep

overlay/usr/share/udhcpc/default.script.d/ntp

@@ -1,12 +1,13 @@
 #!/bin/sh
 
+NTP_DEFAULT_FILE="/etc/default/ntp.conf"
 NTP_WORKING_FILE="/tmp/ntp.conf"
 
 setup_ntp_from_dhcp() {
 	echo "Use DHCP provided NTP servers: $ntpsrv"
 
-	if [ -f "$NTP_WORKING_FILE" ] && [ '444' = "$(stat -c%a $NTP_WORKING_FILE)" ]; then
-		echo "$NTP_WORKING_FILE is read-only, skipping update"
+	if [ -f "$NTP_DEFAULT_FILE" ] && [ '444' = "$(stat -c%a $NTP_DEFAULT_FILE)" ]; then
+		echo "$NTP_DEFAULT_FILE is read-only, skipping update"
 	else
 		echo "Add DHCP provided NTP servers to $NTP_WORKING_FILE"
 		echo $ntpsrv | tr ' ' '\n' | sed 's/^/server /; s/$/ iburst	#added by DHCP/' > $NTP_WORKING_FILE