image-sdk: Rename ivitools variable to sampleappscheckout

Clarify the effect of the variable on the image-sdk recipe by changing
its name.

Signed-off-by: Emanuele Aina <emanuele.aina@collabora.com>

apertis-image-sdk.yaml

@@ -12,7 +12,7 @@
 {{ $demopack := or .demopack "disabled" }}
 
 {{ $size := or .size "20G" }}
-{{ $ivitools := or .ivitools "enabled" }}
+{{ $sampleappscheckout := or .sampleappscheckout "enabled" }}
 {{ $devroot := or .devroot "enabled" }}
 {{ $devroot_arch := or .devroot_arch "armhf" }}
 {{ $devpack := or .devpack (printf "ospack_%s-%s-%s_%s" $suite $devroot_arch "devroot" $timestamp) }}
@@ -96,7 +96,7 @@ actions:
     description: Cleanup /var/lib
     script: scripts/remove_var_lib_parts.sh
 
-  {{ if eq $ivitools "enabled" }}
+  {{ if eq $sampleappscheckout "enabled" }}
   - action: run
     description: Fetch sample app bundle sources
     chroot: true