Make image downloading more resilient

Since the networking can have glitches in CI, let's tolerate a 10 min
downtime to pull images, with 10 seconds between the retries.

Partial-Bug: 1888700
Depends-On: https://review.opendev.org/#/c/742645/
Change-Id: I5ce737669e78c45da1a21e7c227cde53640a733b

roles/oooci-build-images/tasks/main.yaml

@@ -21,6 +21,11 @@
   get_url:
     url: "{{ tripleo_image_source }}"
     dest: "{{ dib_local_image }}"
+    timeout: 20
+  register: result
+  until: result is success
+  retries: 60
+  delay: 10
 
 # The python_v fact is used with vars/common.yaml to set the right
 # overcloud-images file in the build-images.sh.j2 template