openstack-full: manage ICE for Red Hat

ICE is Ceph for Enterprise.

- For CentOS: ensure we use packages from ceph.com repository
  which is the community edition.

- For RHEL7: if CEPH_USERNAME & CEPH_PASSWORD are set, we install ICE
  otherwise we fall back to community edition like CentOS.
Merge pull request #78 from enovance/ceph-packages

openstack-full: manage ICE for Red Hat