When using ipadnsfowardzone with a target host that uses Python 2,
it fails to add new zones due to unicode and str being different on
that version. This patch fixes this behavior ensuring the module
works on both Python verisons 2.7 and 3.x.
This patch allows the modification of the forward zone policy in
an existing DNS Forward Zone, and fixes some issues with `enable`
and `disable` state that prevented correct behavior of `forwardpolicy`.
This patch modify the was forwarders are configured, using two attributes,
`ip_address` and `port`, instead of IPA API internal string representation
of `IP port PORT`.
