* Fix single Redis connection being used across all Sidekiq threads

* Fix tests

Change queue of merge worker from pull to default

must be added to the Sidekiq invokation in your systemd file

The pull queue will handle link crawling, thread resolving, and OStatus
processing. Such tasks are more likely to hang for a longer time (due to
network requests) so it is more sensible to not make the "in-house" tasks
wait for them.

background as well since it's a computationally expensive