h264parse: marks every buffer as header in dash stream
Submitted by Thiago Sousa Santos
every buffer coming out of h264parse is marked as a header.
Easily seen with a debug log 6 of playbin on that file and then grepping:
cat gst.log | grep "avdec_h264-0:sink>" |grep calling |less -RS
Note the flags at the end always contain 0x400