Allow skipping apt usage in package-centric testing

We cannot install any packages in ostree images.

Signed-off-by: Andrej Shadura <andrew.shadura@collabora.co.uk>

lava/group-package-centric-tpl.yaml

@@ -11,6 +11,7 @@ job_name: Run {% raw %}{{job.PACKAGE}}{% endraw %}-in-{{image_name}}
       timeout:
         minutes: 15
       definitions:
+      {%- if skip_apt is not defined %}
       - repository:
           metadata:
             format: Lava-Test Test Definition 1.0
@@ -32,6 +33,7 @@ job_name: Run {% raw %}{{job.PACKAGE}}{% endraw %}-in-{{image_name}}
         from: inline
         path: install-{% raw %}{{job.PACKAGE}}{% endraw %}
         name: install-{% raw %}{{job.PACKAGE}}{% endraw %}
+      {% endif %}
       - repository:
           metadata:
             format: Lava-Test Test Definition 1.0