Replace os-client-config

It was deprecated[1] after the code was merged into openstacksdk[2].

[1] https://review.opendev.org/c/openstack/os-client-config/+/549307
[2] https://review.opendev.org/c/openstack/openstacksdk/+/518128

Change-Id: I57c3489c84a06e788735aa2244907b8ef4875b8c

glanceclient/tests/functional/base.py

@@ -10,13 +10,15 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import glanceclient
+import os
+
 from keystoneauth1 import loading
 from keystoneauth1 import session
-import os
-import os_client_config
+from openstack import config as occ
 from tempest.lib.cli import base
 
+import glanceclient
+
 
 def credentials(cloud='devstack-admin'):
     """Retrieves credentials to run functional tests
@@ -31,7 +33,7 @@ def credentials(cloud='devstack-admin'):
     cloud as that is the current expected behavior.
     """
 
-    return os_client_config.OpenStackConfig().get_one_cloud(cloud=cloud)
+    return occ.OpenStackConfig().get_one(cloud=cloud)
 
 
 class ClientTestBase(base.ClientTestBase):