fail2ban: Add nginx_limit_req to all dicts

Ansible complains if the fail2ban_jails dictionary is missing the
nginx_limit_req key. Adding this as default failse.

Bugfix from: e5773374

Signed-off-by: Leonidas Spyropoulos <artafinde@gmail.com>
2 jobs for add-fail2ban-missing-keys in 57 seconds (queued for 3 seconds)