Previously these type of streams were not returned even if wanted stream was
set to a stream of such. Now they are only skipped if they are not wanted
streams.

Fixes ffplay -sst <stream number> out.ts where stream number is a *_IMPAIRED stream.
Signed-off-by: Marton Balint <cus@passwd.hu>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>