ffmpeg: do not call exit from exit_program()

This should fix  Ticket2116

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 127ff88639e78b9d16fecb973c41b86a843b4fa7)

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>