oggdemux: Fix racy decode error
Copied from https://gitlab.freedesktop.org//gstreamer/gst-plugins-base/-/merge_requests/206
Sometimes the seek to the end of file to determine the duration would trigger a reset of the source pads, that would confuse the decoder downstream and trigger an error. So the proposed fix is to not reset pads when the segment event being processed is the consequence of a seek performed to determine the duration.
Fixes #520 (closed)