Remove all Package<||> dependencies in repo classes

The Exec['xxx'] -> Package<||> dependendies are intended to refresh
package manager metadata but this has several problems:

- With the APT module, it causes dependency cycles because there are
  defines and classes (apt::ppa) that require packages but have to be
  run before Exec['apt_update']

- The puppet-openstack module shouldn't be dictating to users when
  package metadata will be refreshed.  Users should be specify this
  policy outside of the module.

- This will realize any virtal packages that the user has specified in
  any manifest for this node.

This patch also changes the default release from Grizzly to Havana.