oggdemux: validate.http.playback.seek_*.vorbis_theora_1_ogg is often failing

Submitted by Guillaume Desmottes @gdesmott

Link to original bug (#769545)

Description

The validate.http.playback.seek_backward.vorbis_theora_1_ogg validate test is often failing (on Jenkins bot and locally).

It seems the segment pushed after the ACCURATE seek even doesn't report the expected start field:

critical : A segment doesn't have the proper time value after an ACCURATE seek
Detected on oggdemux0:src_2cbf16c0
Detected on multiqueue0:src_0
Detected on theoradec0:src
Detected on inputselector0:src
Detected on streamsynchronizer0:src_0
Detected on vdconv:src
Detected on deinterlace:src
Detected on vqueue:src
Detected on conv:src
Detected on scale:src
Detected on videobalance:src
Detected on conv2:src
Description : If a seek with the ACCURATE flag was accepted, the following segment should have a time value corresponding exactly to the requested start seek time

==== Got criticals, Return value set to 18 ====
Critical error After an accurate seek, got: 0:00:00.000000000 Expected: 0:00:02.496145124
Critical error After an accurate seek, got: 0:00:00.000000000 Expected: 0:00:02.496145124
Critical error After an accurate seek, got: 0:00:00.000000000 Expected: 0:00:02.496145124
Critical error After an accurate seek, got: 0:00:00.000000000 Expected: 0:00:02.496145124
Critical error After an accurate seek, got: 0:00:00.000000000 Expected: 0:00:02.496145124
Critical error After an accurate seek, got: 0:00:00.000000000 Expected: 0:00:02.496145124
Critical error After an accurate seek, got: 0:00:00.000000000 Expected: 0:00:02.496145124
Critical error After an accurate seek, got: 0:00:00.000000000 Expected: 0:00:02.496145124
Critical error After an accurate seek, got: 0:00:00.000000000 Expected: 0:00:02.496145124
Critical error After an accurate seek, got: 0:00:00.000000000 Expected: 0:00:02.496145124
Critical error After an accurate seek, got: 0:00:00.000000000 Expected: 0:00:02.496145124
Critical error After an accurate seek, got: 0:00:00.000000000 Expected: 0:00:02.496145124