Adding the missing HostDomain config option

The ``HostDomain`` config type have been added few months ago [1]
however the config option have been forgotten and this new type
isn't importable.

When we try to import this type without defining a new related cfg
option we get the following issue:

```
AttributeError: module 'oslo_config.cfg' has no attribute 'HostDomain'
```

These changes allow us to import this new type and allow us to use
it in our configs:

```
>>> from oslo_config import cfg
>>> foo = cfg.HostDomain('foo')
>>> foo.type.__call__("1")
...
During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "~/oslo.config/oslo_config/types.py", line 893, in __call__
     raise ValueError(
ValueError: 1 is not a valid host address
>>> foo.type.__call__("host_name")
'host_name'
```

Also properly initialize HostDomain because The HostDomain class wasn't
calling super in it's __init__() method, which resulted in the type_name not
being set properly for instances of that class.

[1] https://opendev.org/openstack/oslo.config/commit/6480356928c9ae6169ea1e5a5b5f1df3d6e0dc75

Change-Id: Ie947803f61ba0ef080018e0447de894a400d7975
Closes-Bug: 1924283

1 files changed, 22 insertions, 0 deletions

diff --git a/oslo_config/cfg.py b/oslo_config/cfg.py
index 39a9878..35f0cfb 100644
--- a/oslo_config/cfg.py
+++ b/oslo_config/cfg.py
@@ -1175,6 +1175,28 @@ class HostAddressOpt(Opt):
                                              **kwargs)
 
 
+class HostDomainOpt(Opt):
+
+    r"""Option for either an IP or a hostname.
+
+    Like HostAddress with the support of _ character.
+
+    Option with ``type`` :class:`oslo_config.types.HostDomain`
+
+    :param name: the option's name
+    :param version: one of either ``4``, ``6``, or ``None`` to specify
+       either version.
+    :param \*\*kwargs: arbitrary keyword arguments passed to :class:`Opt`
+
+    .. versionadded:: 8.6
+    """
+
+    def __init__(self, name, version=None, **kwargs):
+        super(HostDomainOpt, self).__init__(name,
+                                            type=types.HostDomain(version),
+                                            **kwargs)
+
+
 class URIOpt(Opt):
 
     r"""Opt with URI type