Partially restoring code removed by f7064be2 (Bug 2030: Timeout while uploading files to some FTP server using TLS 1.3)

https://winscp.net/tracker/2030

Source commit: 44c1fbf7b3c04eb9018264f4d4cc83f44c27d048

source/filezilla/AsyncSslSocketLayer.cpp

@@ -1005,6 +1005,11 @@ BOOL CAsyncSslSocketLayer::ShutDown(int nHow /*=sends*/)
     }
 
     int res = SSL_shutdown(m_ssl);
+    if (res == 0)
+    {
+      // maybe we do not need to call this at all (as neon does)
+      SSL_shutdown(m_ssl);
+    }
     if (res >= 0)
     {
       if (ShutDownComplete())