Update v3 identity domain configuration tests to work w/ pre-prov

I don't see any limitations by using pre-provisioned
credentials for these tests:

* test_show_default_group_config_and_options
* test_create_domain_config_and_show_config_groups_and_options
* test_create_update_and_delete_domain_config
* test_create_update_and_delete_domain_config_groups_and_opts

Change-Id: I8da97d5998fa50ffce305670cfbac6af74472690
diff --git a/tempest/api/identity/admin/v3/test_domain_configuration.py b/tempest/api/identity/admin/v3/test_domain_configuration.py
index c4e0622..c0b18ca 100644
--- a/tempest/api/identity/admin/v3/test_domain_configuration.py
+++ b/tempest/api/identity/admin/v3/test_domain_configuration.py
@@ -21,6 +21,10 @@
 
 
 class DomainConfigurationTestJSON(base.BaseIdentityV3AdminTest):
+    # NOTE: force_tenant_isolation is true in the base class by default but
+    # overridden to false here to allow test execution for clouds using the
+    # pre-provisioned credentials provider.
+    force_tenant_isolation = False
 
     custom_config = {
         "identity": {