fix(go-libtor-like): make sure we close the os.File

It seems this diff is not necessary to see the real bug, but it
still seems correct to test with better code

Part of ooni/probe#2405

internal/libtor/enabled.go

@@ -138,5 +138,6 @@ func (e *embeddedProcess) EmbeddedControlConn() (net.Conn, error) {
 	if err != nil {
 		return nil, fmt.Errorf("unable to create control socket: %v", err)
 	}
+	file.Close() // net.FileConn duplicates the fd
 	return conn, nil
 }