Add py38 package metadata
Add py38 package metadata

Now that we are running the Victoria tests that include a
voting py38, we can now add the Python 3.8 metadata to the
package information to reflect that support.

Change-Id: I3bd3cb43cd9764bdfe069dfcfd10bd4ed35620d5
Signed-off-by: Sean McGinnis <961eeb09b6d45516665e15b82e013282c4faf575@gmail.com>

openstack/python-ironicclient,openstack/python-ironicclient