Cleanup using about the data_utils module and functions

 HACKING officially discourages symbol import directly because it makes
it harder to track down that a function was imported. Recently, we keep
this rule but there are many code that don't keep it.
 This commit cleanups them.

Change-Id: Ibda1a5e424280bad8535ee27f66dec99bf68f676
diff --git a/tempest/scenario/test_stamp_pattern.py b/tempest/scenario/test_stamp_pattern.py
index 6812d64..a8cedc7 100644
--- a/tempest/scenario/test_stamp_pattern.py
+++ b/tempest/scenario/test_stamp_pattern.py
@@ -19,7 +19,7 @@
 
 from cinderclient import exceptions as cinder_exceptions
 
-from tempest.common.utils.data_utils import rand_name
+from tempest.common.utils import data_utils
 from tempest import exceptions
 from tempest.openstack.common import log as logging
 from tempest.scenario import manager
@@ -75,7 +75,7 @@
         return linux_client.ssh_client
 
     def _create_volume_snapshot(self, volume):
-        snapshot_name = rand_name('scenario-snapshot-')
+        snapshot_name = data_utils.rand_name('scenario-snapshot-')
         volume_snapshots = self.volume_client.volume_snapshots
         snapshot = volume_snapshots.create(
             volume.id, display_name=snapshot_name)