Create a timeout that happens before cleanup (#5438)

* Create a timeout that happens before cleanup

* Remove unnecessary code

* Move a redis call into the method that is running redis:

* Add timelock to beginning of cleanup

lib/sidekiq/api.rb

@@ -887,6 +887,7 @@ module Sidekiq
     # :nodoc:
     # @api private
     def cleanup
+      return 0 unless Sidekiq.redis { |conn| conn.set("process_cleanup", "1", nx: true, ex: 60) }
       count = 0
       Sidekiq.redis do |conn|
         procs = conn.sscan_each("processes").to_a.sort

test/test_api.rb

@@ -664,6 +664,7 @@ describe "API" do
       Sidekiq.redis do |conn|
         conn.sadd("processes", "bar:987")
         conn.sadd("processes", "bar:986")
+        conn.del("process_cleanup")
       end
 
       ps = Sidekiq::ProcessSet.new