catch exceptions as const

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: If18cc0293b52ce5f7f8e068688aa17d28ed27d50
diff --git a/sd_event_loop.cpp b/sd_event_loop.cpp
index 0022769..23f91e4 100644
--- a/sd_event_loop.cpp
+++ b/sd_event_loop.cpp
@@ -68,7 +68,7 @@
         auto reply = bus.call(req);
         reply.read(objs);
     }
-    catch (std::exception& e)
+    catch (const std::exception& e)
     {
         log<level::ERR>("getVLANID: failed to execute/read GetSubTree");
         return 0;
@@ -122,7 +122,7 @@
         auto method_reply = bus.call(method);
         method_reply.read(value);
     }
-    catch (std::exception& e)
+    catch (const std::exception& e)
     {
         log<level::ERR>("getVLANID: failed to execute/read VLAN Id");
         return 0;