No group in inventory for managed: false vms.

If the VM is created as `managed: false`, it is not added to
the inventory. This change ensure no group is created in the
inventory as well.

Fixes whitebox_neutron_tempest_plugin which rely on the inventory.

roles/libvirt_manager/templates/all-inventory.yml.j2

@@ -1,6 +1,6 @@
 all:
   children:
-{% for vm in _cifmw_libvirt_manager_layout.vms.keys() %}
+{% for vm in _cifmw_libvirt_manager_layout.vms.keys() if _cifmw_libvirt_manager_layout.vms[vm].manage | default(true) %}
     {{ (vm == 'crc') | ternary('ocp', vm) }}s:
       vars:
 {% if _cifmw_libvirt_manager_layout.vms[vm].target is defined %}