When changing the adaptivedemux state, gst_adaptive_demux_change_state will try to change the state for all elements on its internal pipeline. One of those is the src element. The src element has a streaming thread which might take the manifest lock (in _src_chain function).

Changing the src state might try to take a lock that the streaming thread is holding. In this case the system deadlocks:
- gst_adaptive_demux_change_state holds the manifest and tries to get a lock in src element to change its state
- src element holds its lock and tries to get the manifest lock

In order to avoid the deadlock, the gst_adaptive_demux_change_state function should not hold the manifest lock while changing the state of its pipeline.