Fixing specs of sidekiq-status to be compatible with Rspec 3.0 and Sidekiq 3.1.4

I fixed the specs to be compliant with the new Rspec syntax and also got the specs running with sidekiq 3.1.4 on ruby 2.1.1.
No, there is no improvement. I just stumbled over this line in combination with the specs and rewrote to check if it is the problem for failure. In the end it wasn't but I thought its clearer to understand it this way.