Transient failure in spec/unicorn/unicorn_spec.rb

As seen in https://gitlab.com/gitlab-org/gitlab-ce/builds/16717300:

  1) Unicorn has a worker that self-terminates on signal SIGQUIT
     Failure/Error: raise "unicorn boot timed out after #{timeout} seconds"

     RuntimeError:
       unicorn boot timed out after 120 seconds
     # ./spec/unicorn/unicorn_spec.rb:80:in `wait_unicorn_boot!'
     # ./spec/unicorn/unicorn_spec.rb:42:in `block (2 levels) in <top (required)>'

  2) Unicorn has a worker that self-terminates on signal SIGTERM
     Failure/Error: raise "unicorn boot timed out after #{timeout} seconds"

     RuntimeError:
       unicorn boot timed out after 120 seconds
     # ./spec/unicorn/unicorn_spec.rb:80:in `wait_unicorn_boot!'
     # ./spec/unicorn/unicorn_spec.rb:42:in `block (2 levels) in <top (required)>'

  3) Unicorn has a worker that self-terminates on signal SIGKILL
     Failure/Error: raise "unicorn boot timed out after #{timeout} seconds"

     RuntimeError:
       unicorn boot timed out after 120 seconds
     # ./spec/unicorn/unicorn_spec.rb:80:in `wait_unicorn_boot!'
     # ./spec/unicorn/unicorn_spec.rb:42:in `block (2 levels) in <top (required)>'

Finished in 27 minutes 38 seconds (files took 22.26 seconds to load)
1248 examples, 3 failures

Failed examples:

rspec './spec/unicorn/unicorn_spec.rb[1:1]' # Unicorn has a worker that self-terminates on signal SIGQUIT
rspec './spec/unicorn/unicorn_spec.rb[1:2]' # Unicorn has a worker that self-terminates on signal SIGTERM
rspec './spec/unicorn/unicorn_spec.rb[1:3]' # Unicorn has a worker that self-terminates on signal SIGKILL