aacparse: Avoid over-skipping when checking LOAS config

aacparse: Avoid over-skipping when checking LOAS config

There might be multiple LOAS config in a row in a full frame. The first
one might be a multi-layer config (which we can't properly parse yet)...
but then followed by a valid (single-layer) one.

The code was previously skipping whole frames (instead of just the LOAS
config we failed to read) resulting in multiple frames (seen up to 6s in
some situation) being dropped before finally getting the configuration.

https://bugzilla.gnome.org/show_bug.cgi?id=758826