client & server: Stability and JingPad Aethercast fixes

Certain OMX video encoder implementations might require the buffer pixels to be arranged fit for the encoder when using Aethercast. To give the encoder what it needs, just allocate server-side (and only server-side) buffers using this flag for correct presentation. Fixes Aethercast on the JingPad.

Also import Ratchanan's fix for proper buffer tracking in case a buffer gets cancelled (already in focal): Since the cancelled buffer is dequeued from the queue_tracker at driver_cancels_buffer(), when returning the same buffer again, it must queued again or various trackings will break. And if driver repeatedly cancels the buffer, this could lead to a crash since queue_tracker will be depleted empty.