rakp12: Clear security sensitive data

As password is sensitive data Clear after use.

Tested:
Verified using ipmitool command
Command: ipmitool -I lanplus -C 17 -p 623 -U root -P <password> -H
         <BMC-IP> user list 1
Response: Displayed user list successfully.

Signed-off-by: Jayaprakash Mutyala <mutyalax.jayaprakash@intel.com>
Change-Id: I662572855fcdc083009a5217042b1018990be9b8
diff --git a/command/rakp12.cpp b/command/rakp12.cpp
index cd84889..1130ee9 100644
--- a/command/rakp12.cpp
+++ b/command/rakp12.cpp
@@ -10,6 +10,7 @@
 #include <algorithm>
 #include <cstring>
 #include <iomanip>
+#include <ipmid/types.hpp>
 #include <phosphor-logging/log.hpp>
 
 using namespace phosphor::logging;
@@ -178,9 +179,7 @@
 
     // Perform user name based lookup
     std::string userName(request->user_name, request->user_name_len);
-    std::string passwd;
-
-    message += "user: " + userName;
+    ipmi::SecureString passwd;
     uint8_t userId = ipmi::ipmiUserGetUserId(userName);
     if (userId == ipmi::invalidUserId)
     {