Switch to use test_utils.call_until_true

test.call_until_true has been deprecated since Newton on Tempest side,
and now Tempest provides test_utils.call_until_true as the stable
library method. So this patch switches to use the stable method before
removing old test.call_until_true on Tempest side.

Change-Id: If8985f511d434af0449992b2bc3540da9b3a0591
diff --git a/ceilometer/tests/tempest/scenario/test_object_storage_telemetry_middleware.py b/ceilometer/tests/tempest/scenario/test_object_storage_telemetry_middleware.py
index 92599a4..a430c2e 100644
--- a/ceilometer/tests/tempest/scenario/test_object_storage_telemetry_middleware.py
+++ b/ceilometer/tests/tempest/scenario/test_object_storage_telemetry_middleware.py
@@ -17,6 +17,7 @@
 from oslo_log import log as logging
 from tempest.common.utils import data_utils
 from tempest import config
+from tempest.lib.common.utils import test_utils
 from tempest.lib import decorators
 from tempest import test
 
@@ -106,9 +107,9 @@
             return (container_name in containers and obj_name in objects)
 
         self.assertTrue(
-            test.call_until_true(_check_samples,
-                                 CONF.telemetry.notification_wait,
-                                 CONF.telemetry.notification_sleep),
+            test_utils.call_until_true(_check_samples,
+                                       CONF.telemetry.notification_wait,
+                                       CONF.telemetry.notification_sleep),
             'Correct notifications were not received after '
             '%s seconds.' % CONF.telemetry.notification_wait)