Remove the need for executing bash script with sudo inside install-gitlab.yml

[jonashackt]

In install-gitlab.yml there´s a shell module invocation with:

  - name: Add the GitLab package repository
    shell: "curl https://packages.gitlab.com/install/repositories/gitlab/gitlab-ce/script.deb.sh | sudo bash"

This could potentially introduce security problems - allthough it is recomended in the GitLab installation docs.