Try downloading the image when inspecting if not available

Currently if you don't have the image on the undercloud, when you try to
run image modify it will fail.  Instead of requiring the user
pre-download the image prior to running the image modify script, let's
attempt a pull if the image doesn't exist.

Change-Id: Ib47331197f27c20281ff86b381cde2a2d8b61519
Closes-Bug: #1835219

tasks/get_original_user.yml

@@ -8,12 +8,27 @@
       delay: 5
       until: source_image_facts.images is defined
       register: source_image_facts
+    - block:
+        - name: Pull Docker image if not currently downloaded
+          docker_image:
+            name: "{{ source_image }}"
+        - name: Inspect image with Docker
+          docker_image_facts:
+            name: "{{ source_image }}"
+          retries: 5
+          delay: 5
+          until: source_image_facts.images is defined
+          register: source_image_facts
+      when: source_image_facts.images | length == 0
     - name: Set original_user with Docker
       set_fact:
         original_user: "{{ source_image_facts.images[0].Config.User }}"
 
 - when: container_build_tool == 'buildah'
   block:
+    - name: Ensure image exists
+      shell: podman image exists {{ source_image }} || podman pull {{ source_image }}
+      become: true
     - name: Inspect image with Buildah
       command: buildah inspect {{ source_image }}
       register: source_image_facts