fix some -Werror,-Wsuggest-override violations

Reviewed By: yfeldblum

Differential Revision: D32187345

fbshipit-source-id: d384aac90c5c0c10580824305ce108e7c0b0e577

folly/DefaultKeepAliveExecutor.h

@@ -30,7 +30,7 @@ namespace folly {
 /// threadsafe.
 class DefaultKeepAliveExecutor : public virtual Executor {
  public:
-  virtual ~DefaultKeepAliveExecutor() { DCHECK(!keepAlive_); }
+  virtual ~DefaultKeepAliveExecutor() override { DCHECK(!keepAlive_); }
 
   template <typename ExecutorT>
   static auto getWeakRef(ExecutorT& executor) {

folly/io/async/AsyncSSLSocket.h

@@ -166,7 +166,7 @@ class AsyncSSLSocket : public AsyncSocket {
           sslSocket_(sslSocket),
           dg_(std::move(dg)) {}
 
-    ~DefaultOpenSSLAsyncFinishCallback() {
+    ~DefaultOpenSSLAsyncFinishCallback() override {
       pipeReader_->setReadCB(nullptr);
       sslSocket_->setAsyncOperationFinishCallback(nullptr);
     }