Add support for option `name_from_ip` in ipadnszone module.

IPA CLI has an option `name_from_ip` that provide a name for a zone
from the reverse IP address, so that it can be used to, for example,
manage PTR DNS records.

This patch adds a similar attribute to ipadnszone module, where it
will try to find the proper zone name, using DNS resolve, or provide
a sane default, if a the zone name cannot be resolved.

The option `name_from_ip` must be used instead of `name` in playbooks,
and it is a string, and not a list.

A new example playbook was added:

    playbooks/dnszone/dnszone-reverse-from-ip.yml

A new test playbook was added:

    tests/dnszone/test_dnszone_name_from_ip.yml