delete volume snapshot is stuck in deleting status when tring to delete more than one at a time from horizon

[Dafna Ron]

I am working with gluster as cinder backend.
created a volume -> created 2 snapshots -> select both snapshot in horizon -> delete

we fail to delete one of the snapshots and the it's stuck in error_deleting with the following error in cinder volume log

013-10-22 14:53:15.454 27438 ERROR cinder.openstack.common.rpc.amqp [req-e45c2a25-35ac-492f-a7fa-9c695f2d63be a660044c9b074450aaa45fba0d641fcc e27aae2598b94dca88cd0408406e0848] Exception during message handling
2013-10-22 14:53:15.454 27438 TRACE cinder.openstack.common.rpc.amqp Traceback (most recent call last):
2013-10-22 14:53:15.454 27438 TRACE cinder.openstack.common.rpc.amqp File "/usr/lib/python2.6/site-packages/cinder/openstack/common/rpc/amqp.py", line 441, in _process_data
2013-10-22 14:53:15.454 27438 TRACE cinder.openstack.common.rpc.amqp **args)
2013-10-22 14:53:15.454 27438 TRACE cinder.openstack.common.rpc.amqp File "/usr/lib/python2.6/site-packages/cinder/openstack/common/rpc/dispatcher.py", line 148, in dispatch
2013-10-22 14:53:15.454 27438 TRACE cinder.openstack.common.rpc.amqp return getattr(proxyobj, method)(ctxt, **kwargs)
2013-10-22 14:53:15.454 27438 TRACE cinder.openstack.common.rpc.amqp File "/usr/lib/python2.6/site-packages/cinder/utils.py", line 808, in wrapper
2013-10-22 14:53:15.454 27438 TRACE cinder.openstack.common.rpc.amqp return func(self, *args, **kwargs)
2013-10-22 14:53:15.454 27438 TRACE cinder.openstack.common.rpc.amqp File "/usr/lib/python2.6/site-packages/cinder/volume/manager.py", line 405, in delete_snapshot
2013-10-22 14:53:15.454 27438 TRACE cinder.openstack.common.rpc.amqp {'status': 'error_deleting'})
2013-10-22 14:53:15.454 27438 TRACE cinder.openstack.common.rpc.amqp File "/usr/lib64/python2.6/contextlib.py", line 23, in __exit__
2013-10-22 14:53:15.454 27438 TRACE cinder.openstack.common.rpc.amqp self.gen.next()
2013-10-22 14:53:15.454 27438 TRACE cinder.openstack.common.rpc.amqp File "/usr/lib/python2.6/site-packages/cinder/volume/manager.py", line 393, in delete_snapshot
2013-10-22 14:53:15.454 27438 TRACE cinder.openstack.common.rpc.amqp self.driver.delete_snapshot(snapshot_ref)
2013-10-22 14:53:15.454 27438 TRACE cinder.openstack.common.rpc.amqp File "/usr/lib/python2.6/site-packages/cinder/volume/drivers/glusterfs.py", line 650, in delete_snapshot
2013-10-22 14:53:15.454 27438 TRACE cinder.openstack.common.rpc.amqp raise exception.GlusterfsException(msg)
2013-10-22 14:53:15.454 27438 TRACE cinder.openstack.common.rpc.amqp GlusterfsException: No snap found with volume-f9d6b98f-8394-4a01-9424-f23897382d87.1493f904-4994-44ed-be1a-8270f5070919 as backing file.
2013-10-22 14:53:15.454 27438 TRACE cinder.openstack.common.rpc.amqp