grubby-bls: use id instead of title to get the default entry

The wrapper is using the title before to store the default entry, but we
are now using the entry id for grub2, so make the wrapper query the id.

Resolves: rhbz#1638103

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

grubby-bls

@@ -127,13 +127,13 @@ get_default_index() {
 
     # GRUB2 and zipl use different fields to set the default entry
     if [[ $bootloader = "grub2" ]]; then
-	title="$default"
+	id="$default"
     else
 	version="$default"
     fi
 
     for i in ${!bls_file[@]}; do
-        if [[ $title = ${bls_title[$i]} || $version = ${bls_version[$i]} ||
+        if [[ $title = ${bls_title[$i]} || $id = ${bls_id[$i]} ||
            $i -eq $index ]]; then
             echo $i
             return