roles/certbot: Reload Apache before cert requests

The Apache service needs to be reloaded after the *certbot* role
configures it to serve the `/.well-known/acme-challenge` path, so that
the changes can take effect before the `certbot` command is run to
request the certificate(s).

roles/certbot/tasks/main.yml

@@ -58,6 +58,7 @@
     dest=/etc/httpd/conf.d/certbot.conf
     mode=0644
   notify: reload httpd
+- meta: flush_handlers
 
 - name: ensure letsencrypt account data are installed
   become: true