Fix: Make sure we have all the metadata streams before adding new traces

Fix: Make sure we have all the metadata streams before adding new traces

The add_one_trace function needs to have a metadata stream for all the
known traces. If it does not, we could end up in situations where we
fetch new streams while adding a trace which causes a lot of problems.

Now we ensure we have all the metadata streams before adding the traces.

Signed-off-by: Julien Desfossez <jdesfossez@efficios.com>
Acked-by: Jonathan Rajotte-Julien <jonathan.rajotte-julien@efficios.com>
Tested-by: Jonathan Rajotte-Julien <jonathan.rajotte-julien@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>