Update az_sig_publish

Co-authored-by: James Le Cuirot <jlecuirot@microsoft.com>

Author: sayanchowdhury

az_sig_publish

@@ -87,7 +87,7 @@ function ensure-vhd-uri-exists() {
   echo "Blob doesn't exist. Downloading flatcar-linux-${FLATCAR_GALLERY_VERSION}-${FLATCAR_CHANNEL}-${FLATCAR_ARCH}"
   # Download the VHD file (only if blob doesn't exist)
   echo "Downloading ${FLATCAR_LOCAL_FILE_URL}..."
-  if ! curl -L -o "/data/${FLATCAR_LOCAL_FILE_NAME}.bz2" "${FLATCAR_LOCAL_FILE_URL}"; then
+  if ! curl -f -L -o "/data/${FLATCAR_LOCAL_FILE_NAME}.bz2" "${FLATCAR_LOCAL_FILE_URL}"; then
     echo "ERROR: Download failed. Exiting"
     exit 1
   fi