Use 'exec' in Unicorn and Sidekiq launch scripts
When running Unicorn or Sidekiq in the foreground this change removes an intermediate /bin/sh process. This makes process supervision in the GitLab Development Kit more reliable.
This change does not affect Omnibus-GitLab (because there we do not use these launch scripts). Installations from source do use the launch scripts but for the standard GitLab init script this change will not make a difference.
Custom installations using Upstart or Systemd may be affected however, because under certain configurations these systems count exactly how many forks happen during process startup, and we are reducing that number by one here.