PEL: Catch exception as const

That's the preferred way when catching exceptions.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: Ib4f27c1de673a99e61468adf261050d9c95172df
diff --git a/extensions/openpower-pels/manager.cpp b/extensions/openpower-pels/manager.cpp
index 20992b3..c6c9243 100644
--- a/extensions/openpower-pels/manager.cpp
+++ b/extensions/openpower-pels/manager.cpp
@@ -1004,7 +1004,7 @@
             {
                 _dataIface->createProgressSRC(srcRefCode, asciiSRC);
             }
-            catch (std::exception& e)
+            catch (const std::exception&)
             {
                 // Exception - may be no boot progress interface on dbus
             }