Updated tasks to use ``systemctl`` for RHEL 7.

Updated tasks to use ``systemctl`` instead of ``service`` to manage
services as well as use OS-version specific service names (e.g.
``firewalld`` versus ``iptables``).

String formatting uses indexes to accommodate older versions of Python.

Also, cleaned up the ``cdn_install`` task by removing its ``subscribe``
and ``install_prerequisites`` calls since these already already handled
by ``product_install``.
Merge pull request #68 from omaciel/rhel-7

Updated tasks to use ``systemctl`` for RHEL 7.
Improve setup provisioning task

Update yum call to not ask for confirmation, update required packages
and silent some commands outputs. Also drop call to network start in
favor of later restart.
Merge pull request #73 from elyezer/improve-setup-provisioning

Improve setup provisioning task