change periodic_task to catch all exceptions including BaseException

the function of periodic_task does not catch all exception so that
all periodic task will die if one periodic task throw BaseException
Closes-Bug: #1730556

Change-Id: I2819cd3644aacac86bc6d12c980d8902f1a71823

oslo_service/periodic_task.py

@@ -218,7 +218,7 @@ class PeriodicTasks(object):
 
             try:
                 task(self, context)
-            except Exception:
+            except BaseException:
                 if raise_on_error:
                     raise
                 LOG.exception(_LE("Error during %(full_task_name)s"),