do not allow node_description to be set at global grid-wide level

salt/sensoroni/defaults.yaml

@@ -6,6 +6,5 @@ sensoroni:
       timeout_ms: 900000
       parallel_limit: 5
     node_checkin_interval_ms: 10000
-    node_description: ''
     sensoronikey:
     soc_host:

salt/sensoroni/soc_sensoroni.yaml

@@ -24,6 +24,8 @@ sensoroni:
     node_description:
       description: Description of the specific node.
       helpLink: sensoroni.html
+      node: True
+      forcedType: string
     sensoronikey:
       description: Shared key for sensoroni authentication.
       helpLink: sensoroni.html