Fix: rotation state marked as completed before relayd has completed

The session rotation state is updated to COMPLETED before the
relay daemon has signaled that its rotation has been completed.
This causes users using the "rotation get_info" API to receive
this status before the session archive is readable on the
relay daemon's end.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>