Update nlohmann::json library to 3.9.0

Cleanup codes.

src/nodemanip.cpp

@@ -113,7 +113,7 @@ int addNodes(std::string link, std::vector<nodeInfo> &allNodes, int groupID, con
                 writeLog(LOG_TYPE_ERROR, "Invalid subscription!");
                 return -1;
             }
-            if(strSub.find("ssd://") == 0)
+            if(startsWith(strSub, "ssd://"))
             {
                 getSubInfoFromSSD(strSub, subInfo);
             }