catch exceptions as const

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I2dc48774ef73fcfbe9287196086f829a6948320d
diff --git a/src/main.cpp b/src/main.cpp
index 2cdb490..98cae3e 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -77,7 +77,7 @@
                 phosphor::logging::entry("RET=%d", ret));
         }
     }
-    catch (std::exception& e)
+    catch (const std::exception& e)
     {
         phosphor::logging::log<phosphor::logging::level::ERR>(e.what());
         return -1;