Description: Cherry pick fix for ionice on OpenVZ (r2242)

--- ltsp-5.3.7.orig/server/ltsp-update-image
+++ ltsp-5.3.7/server/ltsp-update-image
@@ -333,7 +333,7 @@ generate_image () {
     IMAGE="${IMGDIR}/${ARCH}.img"
     rm -f "${IMAGE}.tmp" >/dev/null 2>&1
     test -x /usr/bin/nice && nice=nice || unset nice
-    test -x /usr/bin/ionice && ionice=ionice || unset ionice
+    test -x /usr/bin/ionice && /usr/bin/ionice -c3 true 2>/dev/null && ionice=ionice || unset ionice
     $nice $ionice mksquashfs "${CHROOT}" "${IMAGE}.tmp" $NO_COMP -e cdrom ${EX_DIRS}
     if [ "$?" != "0" ]; then
         rm -f "${IMAGE}.tmp"
