Update git submodules

* Update oslo.config from branch 'master'
  to 6e91dbb2d590fc1706243922c0ed71f6c2fcdf73
  - Merge "Adding the missing HostDomain config option"
  - 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] 6480356928
    
    Change-Id: Ie947803f61ba0ef080018e0447de894a400d7975
    Closes-Bug: 1924283

oslo.config

@@ -1 +1 @@
-Subproject commit 758775c07bc66db3ee6602ecaec53173e89c5acb
+Subproject commit 6e91dbb2d590fc1706243922c0ed71f6c2fcdf73