Another celery.utils.time fix (#518)

For bug #496
To go along with this: 12b7646
and this: #510

Author: loisaidasam

djcelery/backends/database.py

@@ -2,7 +2,10 @@
 
 from celery import current_app
 from celery.backends.base import BaseDictBackend
-from celery.utils.timeutils import maybe_timedelta
+try:
+    from celery.utils.timeutils import maybe_timedelta
+except ImportError:
+    from celery.utils.time import maybe_timedelta
 
 from ..models import TaskMeta, TaskSetMeta