management+util: add 'override' specifier where applicable

Change-Id: Iafb9c2c59026e4268522120f405585ba35fac248
diff --git a/src/management/nfd-control-command.cpp b/src/management/nfd-control-command.cpp
index 307810d..88db4f9 100644
--- a/src/management/nfd-control-command.cpp
+++ b/src/management/nfd-control-command.cpp
@@ -31,6 +31,8 @@
 {
 }
 
+ControlCommand::~ControlCommand() = default;
+
 void
 ControlCommand::validateRequest(const ControlParameters& parameters) const
 {