Fixed scheduled jobs locking

[dmeremyanin]

Move unique key generation to worker class and refactored code a bit.

/cc @krasnoukhov

[krasnoukhov]

Hey @dimko, thanks for refactoring. Could you please describe which exact issue this intended to fix?

[dmeremyanin]

Hi, we don't need to set unique key in redis for scheduled jobs unless unique option is set to :all.
For example:

class UniqueWorker
  include Sidekiq::Worker
  sidekiq_options queue: :unique_queue, unique: true

  def perform(x)
  end
end

at = Time.now.to_f
5.times { Sidekiq::Client.push('class' => UniqueWorker, 'args' => ['args'], 'at' => at) } # Scheduled jobs
assert_equal 5, Sidekiq.redis { |c| c.zcard('schedule') }

This fails on master.

[krasnoukhov]

Ok, this all looks good. Thanks!