Take boost error_code by reference

By convention, we should be following boost here, and passing error_code
by reference, not by value.  This makes our code consistent, and removes
the need for a copy in some cases.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: Id42ea4a90b6685a84818b87d1506c11256b3b9ae
diff --git a/redfish-core/lib/telemetry_service.hpp b/redfish-core/lib/telemetry_service.hpp
index 02d7f38..f9df850 100644
--- a/redfish-core/lib/telemetry_service.hpp
+++ b/redfish-core/lib/telemetry_service.hpp
@@ -39,7 +39,7 @@
         *crow::connections::systemBus, telemetry::service,
         "/xyz/openbmc_project/Telemetry/Reports",
         "xyz.openbmc_project.Telemetry.ReportManager",
-        [asyncResp](const boost::system::error_code ec,
+        [asyncResp](const boost::system::error_code& ec,
                     const dbus::utility::DBusPropertiesMap& ret) {
         if (ec == boost::system::errc::host_unreachable)
         {