Fix cluster creation: missing config schema for CAPI

Change-Id: I7f7b4f494d235cd2f39f22b63e45415249d8d998
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>
diff --git a/osm_nbi/validation.py b/osm_nbi/validation.py
index e31b523..2c2972d 100644
--- a/osm_nbi/validation.py
+++ b/osm_nbi/validation.py
@@ -1129,6 +1129,8 @@
             "type": "string",
             "pattern": "^arn:aws:iam::\\d{12}:role\\/[A-Za-z0-9]+$",
         },
+        # additional cluster configuration parameters
+        "config": object_schema,
     },
     "required": ["vim_account", "name", "k8s_version"],
     "additionalProperties": False,