Fix Sidekiq sleep time for jobs that use replicas

We should sleep based on the time remaining to reach the minimum delay
and not based on the time elapsed from creation.

Changelog: fixed

lib/gitlab/database/load_balancing/sidekiq_server_middleware.rb

@@ -61,8 +61,9 @@ module Gitlab
         end
 
         def sleep_if_needed(job)
-          time_diff = Time.current.to_f - job['created_at'].to_f
-          sleep time_diff if time_diff > 0 && time_diff < MINIMUM_DELAY_INTERVAL
+          remaining_delay = MINIMUM_DELAY_INTERVAL - (Time.current.to_f - job['created_at'].to_f)
+
+          sleep remaining_delay if remaining_delay > 0 && remaining_delay < MINIMUM_DELAY_INTERVAL
         end
 
         def get_wal_locations(job)

spec/lib/gitlab/database/load_balancing/sidekiq_server_middleware_spec.rb

@@ -152,7 +152,7 @@ RSpec.describe Gitlab::Database::LoadBalancing::SidekiqServerMiddleware, :clean_
           let(:elapsed_time) { described_class::MINIMUM_DELAY_INTERVAL - 0.3 }
 
           it 'sleeps until the minimum delay is reached' do
-            expect(middleware).to receive(:sleep).with(be_within(0.01).of(elapsed_time))
+            expect(middleware).to receive(:sleep).with(be_within(0.01).of(described_class::MINIMUM_DELAY_INTERVAL - elapsed_time))
 
             run_middleware
           end