crio: use system default for storage driver by default (#6637)

After host reboot kubelet and crio goes into a loop and no container is started.

storage_driver in crio.conf overrides system defaults in etc/containers/storage.conf

/etc/containers/storage.conf is installed by package containers-common dependency
installed from cri-o (centos7) and contains "overlay".

Hosts already configured with overlay2 should be reconfigured and the
/var/lib/containers content removed.

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

@@ -15,7 +15,10 @@ crio_runc_path: "/usr/bin/runc"
 crio_seccomp_profile: ""
 crio_selinux: "{{ (preinstall_selinux_state == 'enforcing')|lower }}"
 crio_signature_policy: "{% if ansible_os_family == 'ClearLinux' %}/usr/share/defaults/crio/policy.json{% endif %}"
-crio_storage_driver: "overlay2"
+
+# Override system default for storage driver
+# crio_storage_driver: "overlay"
+
 crio_stream_port: "10010"
 
 crio_required_version: "{{ kube_version | regex_replace('^v(?P<major>\\d+).(?P<minor>\\d+).(?P<patch>\\d+)$', '\\g<major>.\\g<minor>') }}"

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

@@ -24,7 +24,9 @@
 
 # Storage driver used to manage the storage of images and containers. Please
 # refer to containers-storage.conf(5) to see all available storage drivers.
+{% if crio_storage_driver is defined %}
 storage_driver = "{{ crio_storage_driver }}"
+{% endif %}
 
 # List to pass options to the storage driver. Please refer to
 # containers-storage.conf(5) to see all available storage options.