delete interface times out in check-tempest-dsvm-neutron

This occurred during a tempest run on https://review.openstack.org/#/c/78459/ (in Keystone). check-tempest-dsvm-neutron failed with a single test failure: tempest.api.compute.v3.servers.test_attach_interfaces.AttachInterfacesV3Test.test_create_list_show_delete_interfaces

Looks like the test gets a token, starts booting an instance:

POST http://127.0.0.1:5000/v2.0/tokens - Status: 200
POST http://127.0.0.1:8774/v3/servers - Status: 202

... this is all probably expected... eventually it does a DELETE:

2014-03-12 20:59:32,797
Request: DELETE http://127.0.0.1:8774/v3/servers/f4433c4f-4d27-492d-8794-77674a634c3f/os-attach-interfaces/f145579d-aaa5-4d44-941c-9856500f65b5
Response Status: 202

Then it starts requesting status... and eventually it gives up:

2014-03-12 21:02:48,016
GET http://127.0.0.1:8774/v3/servers/f4433c4f-4d27-492d-8794-77674a634c3f/os-attach-interfaces
Response Status: 200
Response Body: ... "port_state": "ACTIVE", ... "port_state": "ACTIVE" ... "port_state": "ACTIVE"

The test failed in _test_delete_interface:

File "tempest/api/compute/v3/servers/test_attach_interfaces.py", line 127, in test_create_list_show_delete_interfaces
File "tempest/api/compute/v3/servers/test_attach_interfaces.py", line 96, in _test_delete_interface
Details: Failed to delete interface within the required time: 196 sec.

The timings at the end show the slowpoke:

tempest.api.compute.v3.servers.test_attach_interfaces.AttachInterfacesV3Test.test_create_list_show_delete_interfaces[gate,smoke] 218.999

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Neutron's last entry for the instance in q-svc.txt is

[12/Mar/2014 21:02:52] "GET /v2.0/ports.json?device_id=f4433c4f-4d27-492d-8794-77674a634c3f HTTP/1.1" 200 1912 0.027403

I grepped through the q-svc.txt log file and I don't see anyplace where the DELETE is forwarded on.

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Did the test not wait long enough for the operation to complete? Was the shutdown request ignored?