output/recorder, test/*: invoke encoder_read() after _open()

Make sure the file header gets written at the beginning, before
_write() gets called.

test/run_encoder.c

@@ -106,6 +106,8 @@ int main(int argc, char **argv)
 		return 1;
 	}
 
+	encoder_to_stdout(encoder);
+
 	/* do it */
 
 	while ((nbytes = read(0, buffer, sizeof(buffer))) > 0) {