Revert "ffmpeg: modify tty state when stderr is redirected"

faults in fate otherwise breaks the terminal.
To reproduce, add a abort() into wav_read_header()
run make fate-acodec-adpcm-ima_wav

This reverts commit 92e62f49.

ffmpeg.c

@@ -372,7 +372,7 @@ void term_init(void)
         struct termios tty;
         int istty = 1;
 #if HAVE_ISATTY
-        istty = isatty(0);
+        istty = isatty(0) && isatty(2);
 #endif
         if (istty && tcgetattr (0, &tty) == 0) {
             oldtty = tty;