Correct cron entry for pypimirror.

* modules/pypimirror/manifests/init.pp: An errant change in commit
008fb47 switched pypimirror's update_mirror cron entry from
specifying hour 0 to minute 0 instead. This corrects it back.

Change-Id: Ibedc4e0f823f8bda229da99ed4edc27702118c60
Reviewed-on: https://review.openstack.org/18902
Reviewed-by: Monty Taylor <mordred@inaugust.com>
Approved: James E. Blair <corvus@inaugust.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins