Cinder with purestorage backend fails temporarily with "Volume limit reached." error message

Issue

Running cinder with purestorage backend, the following error message can be observed when repeatedly deleting and creating lots of volumes. This issue happens from time to time only.

2016-08-18 16:32:32.444 27939 WARNING cinder.volume.manager [req-53d7a3a7-f933-4537-b852-dbda225cfe1e 0d3d4279ebdc48619b0a0749b1417fe8 609bba939e3d43fda97d886296f2b861 - - -] Task 'cinder.volume.flows.manager.create_volume.CreateVolume
FromSpecTask;volume:create' (d1571d78-06ba-4568-85b5-3808e430f59a) transitioned into state 'FAILURE' from state 'RUNNING'
2016-08-18 16:32:32.444 27939 TRACE cinder.volume.manager Traceback (most recent call last):
2016-08-18 16:32:32.444 27939 TRACE cinder.volume.manager   File "/usr/lib/python2.7/site-packages/taskflow/engines/action_engine/executor.py", line 67, in _execute_task
2016-08-18 16:32:32.444 27939 TRACE cinder.volume.manager     result = task.execute(**arguments)
2016-08-18 16:32:32.444 27939 TRACE cinder.volume.manager   File "/usr/lib/python2.7/site-packages/cinder/volume/flows/manager/create_volume.py", line 639, in execute
2016-08-18 16:32:32.444 27939 TRACE cinder.volume.manager     **volume_spec)
2016-08-18 16:32:32.444 27939 TRACE cinder.volume.manager   File "/usr/lib/python2.7/site-packages/cinder/volume/flows/manager/create_volume.py", line 613, in _create_raw_volume
2016-08-18 16:32:32.444 27939 TRACE cinder.volume.manager     return self.driver.create_volume(volume_ref)
2016-08-18 16:32:32.444 27939 TRACE cinder.volume.manager   File "/usr/lib/python2.7/site-packages/cinder/volume/drivers/pure.py", line 151, in create_volume
2016-08-18 16:32:32.444 27939 TRACE cinder.volume.manager     self._array.create_volume(vol_name, vol_size)
2016-08-18 16:32:32.444 27939 TRACE cinder.volume.manager   File "/usr/lib/python2.7/site-packages/purestorage/purestorage.py", line 386, in create_volume
2016-08-18 16:32:32.444 27939 TRACE cinder.volume.manager     return self._request("POST", "volume/{0}".format(volume), {"size":size})
2016-08-18 16:32:32.444 27939 TRACE cinder.volume.manager   File "/usr/lib/python2.7/site-packages/purestorage/purestorage.py", line 157, in _request
2016-08-18 16:32:32.444 27939 TRACE cinder.volume.manager     raise PureHTTPError(self._target, self._rest_version, response)
2016-08-18 16:32:32.444 27939 TRACE cinder.volume.manager PureHTTPError: PureHTTPError status code 400 returned by REST version 1.4 at 192.168.1.1: BAD REQUEST
2016-08-18 16:32:32.444 27939 TRACE cinder.volume.manager [{"msg": "Volume limit reached.", "ctx": "volume-60aceab2-9b67-488d-a56b-3b41a30b58a4-cinder"}]
2016-08-18 16:32:32.444 27939 TRACE cinder.volume.manager 
2016-08-18 16:32:32.445 27939 DEBUG taskflow.engines.action_engine.runner [req-53d7a3a7-f933-4537-b852-dbda225cfe1e 0d3d4279ebdc48619b0a0749b1417fe8 609bba939e3d43fda97d886296f2b861 - - -] Discarding failure 'Failure: purestorage.purestorage.PureHTTPError: PureHTTPError status code 400 returned by REST version 1.4 at 192.168.1.1: BAD REQUEST