Ml policy: write data

Author: ldematte

x-pack/plugin/ml/src/main/plugin-metadata/entitlement-policy.yaml

@@ -4,3 +4,6 @@ org.elasticsearch.ml:
       - relative_path: mlmodel.conf
         relative_to: config
         mode: read
+      - relative_path: "ml-local-data/"
+        relative_to: data
+        mode: read_write