[MTL] Connection instability towards add-ons

We are detecting an higher number of errors than expected on the reverse-proxies dedicated to add-ons in the MTL zone. A really small percentage of users may experience trouble to connect to their database. We are investigating.

EDIT 17:45 UTC: we have passed a configuration to try to mitigate the issue. We are watching.

EDIT 18:00 UTC : we have done a rolling reboot of load balancers to give them more capacity.