dcmi: correct return data of Get Configuration Parameter command

When users call "ipmitool dcmi get_conf_param" command, ipmitool shows
paramters are disabled or 0.
```
    DHCP Discovery method    :
        Management Controller ID String is disabled
        Vendor class identifier DCMI IANA and Vendor class-specific \
                                        Informationa are disabled
    Initial timeout interval    : 0 seconds
    Server contact timeout interval    : 0 seconds
    Server contact retry interval    : 0 seconds
```

Those information are incorrect. The root cause of this issue due to the
Get DCMI Configuration Command only returns success value w/o parameter
data.

This commit adds parameter data to the response message.

Tested:
    1. Get DCMI Configuration Parameter
       $ipmitool dcmi get_conf_param
    2. Data are shown as below
        ```
        DHCP Discovery method    :
            Management Controller ID String is enabled
            Vendor class identifier DCMI IANA and Vendor class-specific
                                            Informationa are disabled
        Initial timeout interval    : 4 seconds
        Server contact timeout interval    : 120 seconds
        Server contact retry interval    : 64 seconds
        ```

Change-Id: I0089993062c3c30792786b8e7f0f39f9507f93c3
Signed-off-by: Thang Tran <thuutran@amperecomputing.com>
diff --git a/dcmihandler.cpp b/dcmihandler.cpp
index da6fced..0c0f2bb 100644
--- a/dcmihandler.cpp
+++ b/dcmihandler.cpp
@@ -963,7 +963,7 @@
             return ipmi::responseInvalidFieldRequest();
     }
 
-    return ipmi::responseSuccess();
+    return ipmi::responseSuccess(payload);
 }
 
 static std::optional<uint16_t> readPower(ipmi::Context::ptr& ctx)