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

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"]