Fix device or resource busy when patching IPv6 settings

Author: xrh0905

docker/rootfs/etc/s6-overlay/s6-rc.d/prepare/50-ipv6.sh

@@ -28,7 +28,7 @@ process_folder () {
 	for FILE in $FILES
 	do
 		echo "- ${FILE}"
-		sed -E -i "$SED_REGEX" "$FILE"
+		echo "$(sed -E "$SED_REGEX" "$FILE")" > $FILE
 	done
 
 	# ensure the files are still owned by the npm user