grub2: Use menu_auto_hide=1 to match anaconda

menu_auto_hide=1 is required for the boot_success provided by Fedora's
grub2 package. This will fall back to the previous kernel and show the
usually hidden grub menu when booting fails.

This makes it unnecessary to override the timeout_style and using a
reduced timeout of 1 second for disk images.

config.sh

@@ -41,6 +41,10 @@ if [[ "$kiwi_profiles" != *"Container"* ]] && [[ "$kiwi_profiles" != *"FEX"* ]]
 	echo "GRUB_DISABLE_SUBMENU=true" >> /etc/default/grub
 	## Disable recovery entries to match Fedora
 	echo "GRUB_DISABLE_RECOVERY=true" >> /etc/default/grub
+	## Write `menu_auto_hide=1` into grubenv to match Fedora anaconda installs
+	if [["$kiwi_profiles" != *"Server"* ]]; then
+		grub2-editenv /boot/grub2/grubenv set menu_auto_hide=1
+	fi
 fi
 
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