The AC-3 encoders (both floating- as well as fixed-point) as well as
the EAC-3 encoder share code: All use ff_ac3_encode_init() as well as
ff_ac3_encode_close(). Until ee726e77
ff_ac3_encode_init() called ff_ac3_encode_close() to clean up on error.
Said commit removed this and instead set the FF_CODEC_CAP_INIT_CLEANUP
flag; but it did the latter only for the fixed-point AC-3 encoder and
not for the other two users of ff_ac3_encode_init(). This caused any
already allocated buffer to leak upon a subsequent error for the two
other encoders.

This commit fixes this by adding the FF_CODEC_CAP_INIT_CLEANUP flag
to the other two encoders using ff_ac3_encode_init().
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>