This is already done for every other calls to send_packet. The deadlock occures
since FFMPeg 6.0. The decoder tries to get a buffer from a thread during
the draining process, and blocks trying to get the video decoder stream lock
already heald by the drain function.
Fixes#2383
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/4171>