Don't set all_nodes data as group_vars in check mode
Don't set all_nodes data as group_vars in check mode

Since the "render all_nodes data as group_vars" tasks are skipped when
ansible check is true, we should not run the "set all_nodes data as
group_vars" tasks as well. It was missed and now failing when --check is
used (see bug report).

Change-Id: I2852c8285a0e72d855bfed216b53de6bdeeabe68
Closes-Bug: #1854246

openstack/tripleo-heat-templates,openstack/tripleo-heat-templates