(QENG-967) Disable iptables on el hosts bringup.

Also fixes bug in `disable_iptables` where per-array-element was invoking wrong
method. Looks like `disable_iptables` was originally copied from
`copy_ssh_to_root`

Also adds rspec for Beaker::Hypervisor.configure

Signed-off-by: Wayne <wayne@puppetlabs.com>
Merge pull request #377 from waynr/feature/qeng-967-disable-iptables-on-el-hosts

(QENG-967) Disable iptables on el hosts bringup.