avformat/utils: Fix memleaks in avformat_open_input()

avformat/utils: Fix memleaks in avformat_open_input()

A demuxer might have allocated memory while reading the header. If
reading the header was successfull and an error happens before returning
(e.g. when queueing the attached pictures), the read_close function
would have never been called, so that all those allocations would leak.
This commit changes this.

Furthermore, there would be even more memleaks if the error level was
set to AV_EF_EXPLODE in case there is both metadata and id3v2 metadata.
This has been fixed, too.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: Marton Balint <cus@passwd.hu>