Feature/fix failure

* Resque multi failure backend is still broken on the resque-server; this pull request fixes it
* Fixes a regression introduced in 1.23.1 where if you had previously done something like `Resque.after_fork = [Proc.new {}, Proc.new {}]` your hook would fail attempting to call `#call` on an Array. This broke anyone who is using https://github.com/staugaard/resque-multi-job-forks.