ceilometer-expirer: remove the crontab during upgrade

ceilometer-expirer: remove the crontab during upgrade

When running disabled/ceilometer-expirer.yaml, we want to remove the
crontab that used to run ceilometer-expirer binary in periodic way.
Let's use Puppet to remove this crontab.

We can't easily use Ansible tasks this time, because the Ansible cron
module can only remove Crontabs previously managed by Ansible:
https://docs.ansible.com/ansible/cron_module.html#examples

In this case, Puppet will erase the crontab in Pike. In Queens, we'll be
able to remove these environments files since we wouldn't need it
anymore.

Change-Id: Idb050c3b281d258aea52d6a3ef40441bb9c8bcbe