gnocchi fails with 'tooz redis lock" error

Issue

• gnochi logs files are full of the following errors :

  2017-06-28 13:48:35.684 1002572 WARNING tooz.drivers.redis [-] Unable to heartbeat lock '<tooz.drivers.redis.RedisLock object at 0x7f196c1cf3d0>'
  2017-06-28 13:48:35.684 1002572 ERROR tooz.drivers.redis Traceback (most recent call last):
  2017-06-28 13:48:35.684 1002572 ERROR tooz.drivers.redis   File "/usr/lib/python2.7/site-packages/tooz/drivers/redis.py", line 506, in heartbeat
  2017-06-28 13:48:35.684 1002572 ERROR tooz.drivers.redis     lock.heartbeat()
  2017-06-28 13:48:35.684 1002572 ERROR tooz.drivers.redis   File "/usr/lib/python2.7/site-packages/tooz/drivers/redis.py", line 102, in heartbeat
  2017-06-28 13:48:35.684 1002572 ERROR tooz.drivers.redis     self._lock.extend(self._lock.timeout)
  2017-06-28 13:48:35.684 1002572 ERROR tooz.drivers.redis   File "/usr/lib64/python2.7/contextlib.py", line 35, in __exit__
  2017-06-28 13:48:35.684 1002572 ERROR tooz.drivers.redis     self.gen.throw(type, value, traceback)
  2017-06-28 13:48:35.684 1002572 ERROR tooz.drivers.redis   File "/usr/lib/python2.7/site-packages/tooz/drivers/redis.py", line 54, in _translate_failures
  2017-06-28 13:48:35.684 1002572 ERROR tooz.drivers.redis     cause=e)
  2017-06-28 13:48:35.684 1002572 ERROR tooz.drivers.redis   File "/usr/lib/python2.7/site-packages/tooz/coordination.py", line 763, in raise_with_cause
  2017-06-28 13:48:35.684 1002572 ERROR tooz.drivers.redis     excutils.raise_with_cause(exc_cls, message, *args, **kwargs)
  2017-06-28 13:48:35.684 1002572 ERROR tooz.drivers.redis   File "/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 143, in raise_with_cause
  2017-06-28 13:48:35.684 1002572 ERROR tooz.drivers.redis     six.raise_from(exc_cls(message, *args, **kwargs), kwargs.get('cause'))
  2017-06-28 13:48:35.684 1002572 ERROR tooz.drivers.redis   File "/usr/lib/python2.7/site-packages/six.py", line 692, in raise_from
  2017-06-28 13:48:35.684 1002572 ERROR tooz.drivers.redis     raise value
  2017-06-28 13:48:35.684 1002572 ERROR tooz.drivers.redis ToozError: Cannot extend an unlocked lock