(QENG-845) Beaker junit xml: XML Parsing error

- need to strip out invalid characters from strings before printing to
  xml, these characters are still invalid even if wrapped in a cdata
  tag
Merge pull request #371 from anodelman/xml

(QENG-845) Beaker junit xml: XML Parsing error
(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>