Fix: streaming and snapshot backward compat for relayd < 2.11

Fix backward compatibility of session daemon 2.11 with relayd versions
prior to 2.11.

Session daemon and consumer daemon 2.11 use the "chunk" object to
represent the current output directory. However, both sessiond and
consumerd need to ensure they do not send chunk and rotation commands
to a relayd older than 2.11, and tweak the stream paths accordingly.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>