update doc

docs/usermanual.md

@@ -421,8 +421,8 @@ and
 [Practice: Scenario 3: commands - error](https://github.com/telefonicaid/iotagent-node-lib/blob/master/doc/northboundinteractions.md#scenario-3-commands-error).
 
 MQTT devices commands are always push. For HTTP Devices commands to be push they **must** be provisioned with the
-`endpoint` attribute, that will contain the URL where the IoT Agent will send the received commands. Otherwise the
-command will be poll. When using the HTTP transport, the command handling have two flavours:
+`endpoint` attribute, from device or group device, that will contain the URL where the IoT Agent will send the received
+commands. Otherwise the command will be poll. When using the HTTP transport, the command handling have two flavours:
 
 -   **Push commands**: The request payload format will be a plain JSON, as described in the "Payload" section. The
     device will reply with a 200OK response containing the result of the command in the JSON result format. Example of
@@ -596,7 +596,8 @@ commands and a topic to receive configuration information. This mechanism can be
 configuration flag, `configRetrieval`.
 
 In case of MQTT to retrieve configuration parameters from the Context Broker, it is required that the device should be
-provisioned using "MQTT" as transport key. By default it will be considered "HTTP" as transport.
+provisioned using "MQTT" as transport key, at device or group level. By default it will be considered "HTTP" as
+transport if none transport is defined at device or group level.
 
 The parameter will be given as follows: