[gitlab] Import Gitlab GPG public key

Signed-off-by: ynerant <ynerant@crans.org>

roles/gitlab/tasks/main.yml

 ---
+- name: Install GPG and apt-transport-https
+  apt:
+    update_cache: true
+    install_recommends: false
+    name:
+      - apt-transport-https
+      - gnupg
+  register: apt_result
+  retries: 3
+  until: apt_result is succeeded
+
+- name: Import Gitlab public key
+  apt_key:
+    url: https://packages.gitlab.com/gitlab/gitlab-ee/gpgkey
+
 - name: Configure Gitlab repository
   template:
     src: apt/sources.list.d/gitlab_gitlab-ce.list.j2