Merge branch 'sh-disable-unicorn-sampling-sidekiq' into 'master'

Disable Unicorn sampling in Sidekiq since there are no Unicorn sockets to monitor

See merge request gitlab-org/gitlab-ce!15128

changelogs/unreleased/sh-disable-unicorn-sampling-sidekiq.yml

+---
+title: Disable Unicorn sampling in Sidekiq since there are no Unicorn sockets to monitor
+merge_request:
+author:
+type: performance

config/initializers/8_metrics.rb

@@ -123,7 +123,9 @@ def instrument_classes(instrumentation)
 end
 # rubocop:enable Metrics/AbcSize
 
-Gitlab::Metrics::UnicornSampler.initialize_instance(Settings.monitoring.unicorn_sampler_interval).start
+unless Sidekiq.server?
+  Gitlab::Metrics::UnicornSampler.initialize_instance(Settings.monitoring.unicorn_sampler_interval).start
+end
 
 Gitlab::Application.configure do |config|
   # 0 should be Sentry to catch errors in this middleware