PEL: Add 'override' to derived destructors

cppcheck complains that it is overriding a virtual function in the base
class but isn't marked with override.

Change-Id: I4e03f0524987427e3742672d27b86c71943fab5b
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/extensions/openpower-pels/dbus_watcher.hpp b/extensions/openpower-pels/dbus_watcher.hpp
index 3917e19..5919610 100644
--- a/extensions/openpower-pels/dbus_watcher.hpp
+++ b/extensions/openpower-pels/dbus_watcher.hpp
@@ -73,7 +73,7 @@
 {
   public:
     PropertyWatcher() = delete;
-    ~PropertyWatcher() = default;
+    ~PropertyWatcher() override = default;
     PropertyWatcher(const PropertyWatcher&) = delete;
     PropertyWatcher& operator=(const PropertyWatcher&) = delete;
     PropertyWatcher(PropertyWatcher&&) = delete;
@@ -254,7 +254,7 @@
 {
   public:
     InterfaceWatcher() = delete;
-    ~InterfaceWatcher() = default;
+    ~InterfaceWatcher() override = default;
     InterfaceWatcher(const InterfaceWatcher&) = delete;
     InterfaceWatcher& operator=(const InterfaceWatcher&) = delete;
     InterfaceWatcher(InterfaceWatcher&&) = delete;