Add mock method for security protocol

Summary: as title

Reviewed By: Orvid

Differential Revision: D9568603

fbshipit-source-id: b5ce1ba8163af87f3ec6369407e3f8546e80afb1

folly/io/async/test/MockAsyncTransport.h

@@ -68,6 +68,7 @@ class MockAsyncTransport : public AsyncTransportWrapper {
   MOCK_METHOD1(
       setReplaySafetyCallback,
       void(AsyncTransport::ReplaySafetyCallback*));
+  MOCK_CONST_METHOD0(getSecurityProtocol, std::string());
 };
 
 class MockReplaySafetyCallback : public AsyncTransport::ReplaySafetyCallback {