message: [web] improve add/delete prefix functionality
diff: @@ -180,8 +180,14 @@ std::string WpanService::HandleAddPrefixRequest(const std::string &aAddPrefixReq
  prefix = root["prefix"].asString();
  defaultRoute = root["defaultRoute"].asBool();
  + if (prefix.find('/') == std::string::npos)
  + {
  + prefix += "/64";
  + }
  +
  VerifyOrExit(client.Execute("prefix add %s paso%s", prefix.c_str(), (defaultRoute ? "r" : "")) != nullptr,
  ret = kWpanStatus_SetGatewayFailed);
  + VerifyOrExit(client.Execute("netdata register") != nullptr, ret = kWpanStatus_SetGatewayFailed);
  exit:
  root.clear();
  @@ -212,7 +218,13 @@ std::string WpanService::HandleDeletePrefixRequest(const std::string &aDeleteReq
  VerifyOrExit(reader.parse(aDeleteRequest.c_str(), root) == true, ret = kWpanStatus_ParseRequestFailed);
  prefix = root["prefix"].asString();
  + if (prefix.find('/') == std::string::npos)
  + {
  + prefix += "/64";
  + }
  +
  VerifyOrExit(client.Execute("prefix remove %s", prefix.c_str()) != nullptr, ret = kWpanStatus_SetGatewayFailed);
  + VerifyOrExit(client.Execute("netdata register") != nullptr, ret = kWpanStatus_SetGatewayFailed);
  exit:
  root.clear();
  