Temporarily disable UCA usage in OpenStack-CI

OpenStack-CI does not have Ubuntu Cloud Archive (UCA) mirrors at this stage.
The implementation of Ic1e7619b48a9b12ba876f83507497cf1e557223a set the
usage of UCA for nova to be the default, which is good for production
environments.

This patch temporarily disables its usage in OpenStack-CI while the mirror
of UCA is arranged in OpenStack-Infra.

Change-Id: I0aec0447e1faf5ae21ce542945082079d3a59727

tests/roles/bootstrap-host/tasks/prepare_aio_config.yml

@@ -118,6 +118,16 @@
   tags:
     - generate_secrets
 
+- name: Detect whether the host is an OpenStack-CI host
+  stat:
+    path: /etc/nodepool
+  register: nodepool_dir
+
+- name: Disable nova using UCA in OpenStack-CI
+  set_fact:
+    nova_uca_enable: False
+  when: nodepool_dir.stat.exists
+
 - name: Determine if the host has a global pip config file
   stat:
     path: /etc/pip.conf

tests/roles/bootstrap-host/templates/user_variables.aio.yml.j2

@@ -98,3 +98,8 @@ apply_security_hardening: true
 ## Wheel mirrors for the repo_build to use
 repo_build_pip_extra_indexes: {{ repo_build_pip_extra_indexes }}
 {% endif %}
+
+{% if nova_uca_enable is defined %}
+## TODO(odyssey4me) Remove this once OpenStack-Infra has UCA mirrors
+nova_uca_enable: {{ nova_uca_enable }}
+{% endif %}