VLC seems to generate access units with extra AUDs. In #526, the below
sequence is seen:
AUD | SPS | PPS | SPS | PPS | AUD | SEI | SEI | SEI | IDR_SLICE
Previously we exit early when seeing AUD, which results in delayed
processing of the access unit.
The behavior is changed to continue processing the following NAL units
to workaround the content issue.
Closes#526.
Change-Id: I80f571c0711c6db1337eb393fce36fae5432b6c5