Allow containerd root and state path to be configured (#7098)

roles/container-engine/containerd/defaults/main.yml

@@ -1,4 +1,9 @@
 ---
+# The root directory for containerd metadata
+containerd_metadata_root_dir: /var/lib/containerd
+# The state directory for containerd
+containerd_state_dir: /run/containerd
+
 containerd_config:
   grpc:
     max_recv_message_size: 16777216

roles/container-engine/containerd/templates/config.toml.j2

@@ -1,3 +1,8 @@
+# persistent data location
+root = "{{ containerd_metadata_root_dir }}"
+# runtime state information
+state = "{{ containerd_state_dir }}"
+
 # Kubernetes doesn't use containerd restart manager.
 disabled_plugins = ["restart"]