smtp_enable_starttls_auto cannot be set to false

Actionmailer has the default setting of enable_starttls_auto: true.

If you attempt to set gitlab_rails['smtp_enable_starttls_auto'] = false in the gitlab.rb, the chef script skips over the line entirely because it resolves to false (see https://gitlab.com/gitlab-org/omnibus-gitlab/blob/master/files/gitlab-cookbooks/gitlab/templates/default/smtp_settings.rb.erb ).

This makes it impossible to disable enable_starttls_auto in omnibus without editing the generated configs after they are built.