[Locust] Locust show strange data with new FlightsInSub.py

[the-glu]

Describe the bug

When running FlightsInSub, there is a strange bump in graphs, whatever the datastore, number of nodes or latency parameters used.

This happens when the Subscriber client is creating the subscription. However, this don't match real performance of SCD client:

To reproduce
Steps to reproduce the behavior:

Run loadtest/locust_files/FlightsInSub.py

Possible solution

Either create the subscriptions differently (and ensure they are created at the begining of the test) or exclude Subscriber from tests.