Description of problem:
These tempest classes fail to set up across several virthost CI jobs:

.setUpClass (tempest.api.identity.admin.v3.test_credentials.CredentialsTestJSON)
.setUpClass (tempest.api.identity.admin.v3.test_domains.DomainsTestJSON)
.setUpClass (tempest.api.identity.admin.v3.test_services.ServicesTestJSON) 
.setUpClass (tempest.api.identity.admin.v3.test_domains.DefaultDomainTestJSON)
.setUpClass (tempest.api.identity.admin.v3.test_endpoints.EndPointsTestJSON)
.setUpClass (tempest.api.identity.admin.v3.test_trusts.TrustsV3TestJSON)
.setUpClass (tempest.api.identity.admin.v3.test_policies.PoliciesTestJSON)
.setUpClass (tempest.api.identity.admin.v3.test_groups.GroupsV3TestJSON)
.setUpClass (tempest.api.identity.v3.test_api_discovery.TestApiDiscovery)
.setUpClass (tempest.api.identity.admin.v3.test_regions.RegionsTestJSON)
.setUpClass (tempest.api.identity.admin.v3.test_roles.RolesV3TestJSON)

The stacktrace is similar for each; here is the stacktrace from the last item in the above list:
Traceback (most recent call last):
testtools.testresult.real._StringException: Traceback (most recent call last):
  File "/home/stack/tempest/tempest/test.py", line 262, in setUpClass
    six.reraise(etype, value, trace)
  File "/home/stack/tempest/tempest/test.py", line 250, in setUpClass
    cls.setup_credentials()
  File "/home/stack/tempest/tempest/test.py", line 347, in setup_credentials
    credential_type=credentials_type)
  File "/home/stack/tempest/tempest/test.py", line 518, in get_client_manager
    creds = getattr(cred_provider, credentials_method)()
  File "/home/stack/tempest/tempest/common/dynamic_creds.py", line 264, in get_primary_creds
    return self.get_credentials('primary')
  File "/home/stack/tempest/tempest/common/dynamic_creds.py", line 256, in get_credentials
    credentials.tenant_id)
  File "/home/stack/tempest/tempest/common/dynamic_creds.py", line 172, in _create_network_resources
    network = self._create_network(network_name, tenant_id)
  File "/home/stack/tempest/tempest/common/dynamic_creds.py", line 194, in _create_network
    name=name, tenant_id=tenant_id)
  File "/usr/lib/python2.7/site-packages/tempest_lib/services/network/networks_client.py", line 21, in create_network
    return self.create_resource(uri, post_data)
  File "/usr/lib/python2.7/site-packages/tempest_lib/services/network/base.py", line 60, in create_resource
    resp, body = self.post(req_uri, req_post_data)
  File "/usr/lib/python2.7/site-packages/tempest_lib/common/rest_client.py", line 259, in post
    return self.request('POST', url, extra_headers, headers, body)
  File "/usr/lib/python2.7/site-packages/tempest_lib/common/rest_client.py", line 627, in request
    headers=headers, body=body)
  File "/usr/lib/python2.7/site-packages/tempest_lib/common/rest_client.py", line 526, in _request
    req_url, method, headers=req_headers, body=req_body)
  File "/usr/lib/python2.7/site-packages/tempest_lib/common/rest_client.py", line 557, in raw_request
    headers=headers, body=body)
  File "/usr/lib/python2.7/site-packages/tempest_lib/common/http.py", line 25, in request
    return super(ClosingHttp, self).request(*args, **new_kwargs)
  File "/usr/lib/python2.7/site-packages/httplib2/__init__.py", line 1620, in request
    (response, content) = self._request(conn, authority, uri, request_uri, method, body, headers, redirections, cachekey)
  File "/usr/lib/python2.7/site-packages/httplib2/__init__.py", line 1362, in _request
    (response, content) = self._conn_request(conn, request_uri, method, body, headers)
  File "/usr/lib/python2.7/site-packages/httplib2/__init__.py", line 1318, in _conn_request
    response = conn.getresponse()
  File "/usr/lib64/python2.7/httplib.py", line 1039, in getresponse
    raise ResponseNotReady()
httplib.ResponseNotReady