Set ENABLE_LOAD_BALANCING_FOR_SIDEKIQ=true on staging

We should set environment varialbe ENABLE_LOAD_BALANCING_FOR_SIDEKIQ to true in order to enable load balancing for Sidekiq.

This environment variable will only enable load balancing. All workers will still default to :always data consistency - the worker is required to use primary!

#325520 (comment 534618388)

NOTE:

Prior to this, we will still need to:

Edited by Nikola Milojevic