Add the relayd create session command

Add the relayd create session command

This is needed in order to fix a specific condition of the data pending
where we need to have streams associated with a session and this command
will be used for new feature in the future.

Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: David Goulet <dgoulet@efficios.com>