Allow for single tempest image upload

If 'tempest_images' has been overridden to only contain a single image,
setting a fact for a secondary image will fail since it always expects
'tempest_image_create' to contain two elements. Instead, set the
'tempest_glance_image_id_2' fact as the last element.

Change-Id: If4bbd73f70bfb59695bb7d5f167ed6555e6de16a
(cherry picked from commit 540a6be329)

tasks/tempest_resources.yml

@@ -13,6 +13,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+- name: Ensures you have at least one image to upload
+  assert:
+    that:
+      - "tempest_images | length > 0"
+  when:
+    - tempest_service_available_glance | bool
+
 - name: Create deployment-host tempest_image_dir
   file:
     path: "{{ tempest_image_dir }}"
@@ -70,7 +77,7 @@
 - name: Store first tempest image id
   set_fact:
     tempest_glance_image_id_1: "{{ tempest_service_available_glance | ternary(tempest_image_create['results'][0]['id'], '') }}"
-    tempest_glance_image_id_2: "{{ tempest_service_available_glance | ternary(tempest_image_create['results'][1]['id'], '') }}"
+    tempest_glance_image_id_2: "{{ tempest_service_available_glance | ternary(tempest_image_create['results'][-1]['id'], '') }}"
 
 - name: Ensure tempest tenants
   keystone: