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/include/hostname_monitor.hpp b/include/hostname_monitor.hpp
index f0d8bdf..ed719d5 100644
--- a/include/hostname_monitor.hpp
+++ b/include/hostname_monitor.hpp
@@ -19,7 +19,7 @@
 inline void installCertificate(const std::filesystem::path& certPath)
 {
     crow::connections::systemBus->async_method_call(
-        [certPath](const boost::system::error_code ec) {
+        [certPath](const boost::system::error_code& ec) {
         if (ec)
         {
             BMCWEB_LOG_ERROR << "Replace Certificate Fail..";