grubby-bls: set saved_entry to id instead of title on set-default

The grubby wrapper sets the saved_entry in grubenv to the entry title
field since that's done by grubby. But for BLS the id is the filename
without the .conf extension, this saved_entry is set to this when a
new kernel is installed.

So for consistency also use the entry id for the --set-default option.

Related: rhbz#1638103

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>

grubby-bls

@@ -376,7 +376,7 @@ set_default_bls() {
     local index=($(param_to_indexes "$1"))
 
     if [[ $bootloader = grub2 ]]; then
-        grub2-editenv "${env}" set saved_entry="${bls_title[$index]}"
+        grub2-editenv "${env}" set saved_entry="${bls_id[$index]}"
     else
         local default="${bls_version[$index]}"
         local current="$(grep '^default=' ${zipl_config} | sed -e 's/^default=//')"