Switching to oslo importutils in the stress tests

The importutils is helper module for dynamic class and module,
 loading.

The importutils is compatible with python 2.6 and it is
used in multiple other openstack projects.

The previously used importlib defined with python 2.7.

Change-Id: I4e99ccf9d51cea28584c9d28a4aceab633b3f998
diff --git a/openstack-common.conf b/openstack-common.conf
index 8568f22..ff84404 100644
--- a/openstack-common.conf
+++ b/openstack-common.conf
@@ -4,6 +4,7 @@
 module=install_venv_common
 module=lockutils
 module=log
+module=importlib
 
 # The base module to hold the copy of openstack.common
 base=tempest
diff --git a/tempest/stress/driver.py b/tempest/stress/driver.py
index d170eb8..c4c2041 100644
--- a/tempest/stress/driver.py
+++ b/tempest/stress/driver.py
@@ -12,7 +12,6 @@
 #    See the License for the specific language governing permissions and
 #    limitations under the License.
 
-import importlib
 import logging
 import multiprocessing
 import time
@@ -21,6 +20,7 @@
 from tempest.common import ssh
 from tempest.common.utils.data_utils import rand_name
 from tempest import exceptions
+from tempest.openstack.common import importutils
 from tempest.stress import cleanup
 
 admin_manager = clients.AdminManager()
@@ -93,11 +93,6 @@
     return None
 
 
-def get_action_object(path):
-    (module_part, _, obj_name) = path.rpartition('.')
-    return getattr(importlib.import_module(module_part), obj_name)
-
-
 def stress_openstack(tests, duration, max_runs=None):
     """
     Workload driver. Executes an action function against a nova-cluster.
@@ -131,7 +126,7 @@
                                           password="pass",
                                           tenant_name=tenant_name)
 
-            test_obj = get_action_object(test['action'])
+            test_obj = importutils.import_class(test['action'])
             test_run = test_obj(manager, logger, max_runs)
 
             kwargs = test.get('kwargs', {})