Replace cfn-hup cron job with os-collect-config

Os-collect-config is meant as a replacement for cfn-hup. The @reboot job
can go because os-collect-config will be run when the system is booted.
The periodic job is handled by os-collect-config's default behaviour of
running its command (by default, os-refresh-config) whenever any of its
metadata sources change.

Change-Id: Id768927ddfc4e7b4873fac347905e44458fd341a