rdo-manager: unable to delete the failed overcloude deployment.

Environment:

instack-0.0.6-post6.el7.centos.noarch
instack-undercloud-0.0.0-post1739.el7.centos.noarch

Steps to reproduce:
1. Attempt to deploy an overcloud.
2. Attempt to delete the deployed/failed overcloud.


Result:
Note: This isn't always reproducible.

heat stack-list
+--------------------------------------+------------+---------------+----------------------+
| id                                   | stack_name | stack_status  | creation_time        |
+--------------------------------------+------------+---------------+----------------------+
| 9d2d5b78-312f-451e-8cf7-10bb293d1517 | overcloud  | DELETE_FAILED | 2015-05-14T14:01:27Z |



Get this in the /var/log/heat/heat-api.log:


==> /var/log/heat/heat-api.log <==
RESP BODY: {"token": {"methods": ["password", "token"], "roles": [{"id": "9fe2ff9ee4384b1894a90878d3e92bab", "name": "_member_"}, {"id": "b689936f25734588b2607de27fd2dce2", "name": "admin"}], "expires_at": "2015-05-14T17:10:23.000000Z", "project": {"domain": {"id": "default", "name": "Default"}, "id": "e9ea1eb55ace43688264978ca0c904d7", "name": "admin"}, "catalog": "<removed>", "extras": {}, "user": {"domain": {"id": "default", "name": "Default"}, "id": "f9c296cefc564efdb7647e7694719475", "name": "admin"}, "audit_ids": ["V1AvM4ZMRlGSGAop3qcjxA"], "issued_at": "2015-05-14T16:10:24.007233"}}                                           
 _http_log_response /usr/lib/python2.7/site-packages/keystoneclient/session.py:224                                                                                                                                   
2015-05-14 12:10:24.214 21461 DEBUG heat.openstack.common.policy [req-9dc6b992-91de-47c3-9cc6-32fba98952d8 - admin] Rules successfully reloaded _load_policy_file /usr/lib/python2.7/site-packages/heat/openstack/common/policy.py:295                                                                                                                                                                                                    
2015-05-14 12:10:24.215 21461 INFO heat.openstack.common.policy [req-9dc6b992-91de-47c3-9cc6-32fba98952d8 - admin] Can not find policy directory: policy.d                                                           
2015-05-14 12:10:24.216 21461 DEBUG heat.common.wsgi [req-9dc6b992-91de-47c3-9cc6-32fba98952d8 - admin] Calling <heat.api.openstack.v1.stacks.StackController object at 0x42f89d0> : index __call__ /usr/lib/python2.7/site-packages/heat/common/wsgi.py:647                                                                                                                                                                              
2015-05-14 12:10:24.217 21461 INFO heat.openstack.common.policy [req-9dc6b992-91de-47c3-9cc6-32fba98952d8 - admin] Can not find policy directory: policy.d                                                           
2015-05-14 12:10:24.218 21461 DEBUG oslo_messaging._drivers.amqpdriver [req-9dc6b992-91de-47c3-9cc6-32fba98952d8 - admin] MSG_ID is 5850e391b4ce45a58ded1b336edc0091 _send /usr/lib/python2.7/site-packages/oslo_messaging/_drivers/amqpdriver.py:311                                                                                                                                                                                     
2015-05-14 12:10:24.219 21461 DEBUG oslo_messaging._drivers.amqp [req-9dc6b992-91de-47c3-9cc6-32fba98952d8 - admin] UNIQUE_ID is 1bb42c9b5847414db1f880d17e333287. _add_unique_id /usr/lib/python2.7/site-packages/oslo_messaging/_drivers/amqp.py:258                                                                                                                                                                                    
2015-05-14 12:10:24.313 21461 DEBUG heat.common.serializers [req-9dc6b992-91de-47c3-9cc6-32fba98952d8 - admin] JSON response : {"stacks": [{"description": "No description", "parent": null, "stack_status_reason": "Resource DELETE failed: ResourceUnknownStatus: Resource failed - Unknown status FAILED due to \"Resource DELETE failed: ResourceUnknownStatus: Resource failed - Unknown status FAILED due to \"Resource DELETE failed: Error: Server ov-l5jmbyi5jk-0-tlujyphl7k5c-NovaCompute-uh5tsfwozbpa delete failed: (500) Build of instance 8a891025-9c5b-4361-8096-cb4d7a4a3641 aborted: Failed to allocate the network(s), not rescheduling.\"\"", "stack_name": "overcloud", "stack_user_project_id": "e9ea1eb55ace43688264978ca0c904d7", "tags": null, "creation_time": "2015-05-14T14:01:27Z", "links": [{"href": "http://192.0.2.1:8004/v1/e9ea1eb55ace43688264978ca0c904d7/stacks/overcloud/9d2d5b78-312f-451e-8cf7-10bb293d1517", "rel": "self"}], "updated_time": null, "stack_owner": "admin", "stack_status": "DELETE_FAILED", "id": "9d2d5b78-312f-451e-8cf7-10bb293d1517"}]} to_json /usr/lib/python2.7/site-packages/heat/common/serializers.py:42
2015-05-14 12:10:24.314 21461 INFO eventlet.wsgi.server [req-9dc6b992-91de-47c3-9cc6-32fba98952d8 - admin] 192.0.2.1 - - [14/May/2015 12:10:24] "GET /v1/e9ea1eb55ace43688264978ca0c904d7/stacks HTTP/1.1" 200 1148 0.227526


Expected result:
The overcloud deployment should be deleted.