cri-o: add variable to configure unsecure pull

By default do not allow "unqualified" (without a registry) images
because it is considered unsecure and subject to mitm attacks.

To enable insecure pull configure for example:

crio_registries:
  - "docker.io"
  - "quay.io"

roles/container-engine/cri-o/defaults/main.yml

@@ -6,6 +6,11 @@ crio_enable_metrics: false
 crio_log_level: "info"
 crio_metrics_port: "9090"
 crio_pause_image: "{{ pod_infra_image_repo }}:{{ pod_infra_version }}"
+
+# Trusted registries to pull unqualified images (e.g. alpine:latest) from
+# By default unqualified images are not allowed for security reasons
+crio_registries: []
+
 crio_runc_path: "/usr/bin/runc"
 crio_seccomp_profile: ""
 crio_selinux: "{{ (preinstall_selinux_state == 'enforcing')|lower }}"

roles/container-engine/cri-o/templates/crio.conf.j2

@@ -350,8 +350,11 @@ image_volumes = "mkdir"
 # compatibility reasons. Depending on your workload and usecase you may add more
 # registries (e.g., "quay.io", "registry.fedoraproject.org",
 # "registry.opensuse.org", etc.).
-#registries = [
-# ]
+registries = [
+  {% for registry in crio_registries %}
+  "{{ registry }}",
+  {% endfor %}
+]
 
 
 # The crio.network table containers settings pertaining to the management of