[scripts] delete existing .sha256 files from CDROOT_DIR/boot

scripts/pre_iso_script_livecd_hash.sh

@@ -22,12 +22,9 @@ fi
 
 # files inside /boot now
 if [ -d "${CDROOT_DIR}/boot" ]; then
+	# delete existing .sha256 files
+	find "${CDROOT_DIR}/boot" -name "*.sha256" -delete
 	for bootfile in "${CDROOT_DIR}"/boot/* ; do
-		endswith_sha256=$(echo "${bootfile}" | grep "\.sha256$")
-		if [ -n "${endswith_sha256}" ]; then
-			# skip .sha256 file
-			continue
-		fi
 		if [ -f "${bootfile}" ]; then
 			echo "Doing ${bootfile}..."
 			boot_dir=$(dirname "${bootfile}")