Fix: send per-pid session id in channel creation

The registry indexing for per-pid sessions is done with a per-pid session
id. So for per-pid buffers, we need to send the per-pid session id to the
consumer in order to give it enough information if it needs to request
metadata later.

Signed-off-by: Julien Desfossez <jdesfossez@efficios.com>
WIP snapshot metadata

deadlock approaching

Signed-off-by: Julien Desfossez <jdesfossez@efficios.com>