gitlab: set docker's log driver to none

No need to duplicate the logs from /srv/gitlab/logs/.

roles/gitlab/tasks/main.yml

@@ -19,6 +19,7 @@
     network_mode: host
     pull: true
     restart_policy: always
+    log_driver: none
     env:
       # See https://gitlab.com/gitlab-org/omnibus-gitlab/blob/master/files/gitlab-config-template/gitlab.rb.template
       # 1. In order to figure out what needs to go into 'idp_cert_fingerprint', run