Looking at logs from https://review.openstack.org/#/c/45766/ at
http://logs.openstack.org/66/45766/1/check/gate-tempest-devstack-vm-large-ops/a9795a0/

The test error:
BuildErrorException: Server %(server_id)s failed to build and is in ERROR status
Details: <Server: scenario-server-185564612-b5044da7-0f18-476b-a064-2014b2ab391e> failed to get to expected status.                           In ERROR state.

seems to be caused by:
screen-n-cpu.txt.gz:2013-10-08 18:51:31.843 ERROR nova.compute.manager [req-4314b9da-9257-4935-9660-044e13f70d93 tempest.scenario.manager165361106-user tempest.scenario.manager165361106-tenant] [instance: b5044da7-0f18-476b-a064-2014b2ab391e] Error: Timeout while waiting on RPC response - topic: "network", RPC method: "allocate_for_instance" info: "<unknown>"
screen-n-sch.txt.gz:2013-10-08 18:51:31.889 ERROR nova.scheduler.filter_scheduler [req-4314b9da-9257-4935-9660-044e13f70d93 tempest.scenario.manager165361106-user tempest.scenario.manager165361106-tenant] [instance: b5044da7-0f18-476b-a064-2014b2ab391e] Error from last host: devstack-precise-hpcloud-az3-561338 (node devstack-precise-hpcloud-az3-561338): [u'Traceback (most recent call last):\n', u'  File "/opt/stack/new/nova/nova/compute/manager.py", line 1039, in _build_instance\n    set_access_ip=set_access_ip)\n', u'  File "/opt/stack/new/nova/nova/compute/manager.py", line 1448, in _spawn\n    network_info.wait(do_raise=True)\n', u'  File "/opt/stack/new/nova/nova/network/model.py", line 398, in wait\n    self[:] = self._gt.wait()\n', u'  File "/usr/local/lib/python2.7/dist-packages/eventlet/greenthread.py", line 168, in wait\n    return self._exit_event.wait()\n', u'  File "/usr/local/lib/python2.7/dist-packages/eventlet/event.py", line 116, in wait\n    return hubs.get_hub().switch()\n', u'  File "/usr/local/lib/python2.7/dist-packages/eventlet/hubs/hub.py", line 187, in switch\n    return self.greenlet.switch()\n', u'  File "/usr/local/lib/python2.7/dist-packages/eventlet/greenthread.py", line 194, in main\n    result = function(*args, **kwargs)\n', u'  File "/opt/stack/new/nova/nova/compute/manager.py", line 1230, in _allocate_network_async\n    dhcp_options=dhcp_options)\n', u'  File "/opt/stack/new/nova/nova/network/api.py", line 93, in wrapped\n    return func(self, context, *args, **kwargs)\n', u'  File "/opt/stack/new/nova/nova/network/api.py", line 49, in wrapper\n    res = f(self, context, *args, **kwargs)\n', u'  File "/opt/stack/new/nova/nova/network/api.py", line 300, in allocate_for_instance\n    nw_info = self.network_rpcapi.allocate_for_instance(context, **args)\n', u'  File "/opt/stack/new/nova/nova/network/rpcapi.py", line 184, in allocate_for_instance\n    macs=jsonutils.to_primitive(macs))\n', u'  File "/opt/stack/new/nova/nova/rpcclient.py", line 85, in call\n    return self._invoke(self.proxy.call, ctxt, method, **kwargs)\n', u'  File "/opt/stack/new/nova/nova/rpcclient.py", line 63, in _invoke\n    return cast_or_call(ctxt, msg, **self.kwargs)\n', u'  File "/opt/stack/new/nova/nova/openstack/common/rpc/proxy.py", line 130, in call\n    exc.info, real_topic, msg.get(\'method\'))\n', u'Timeout: Timeout while waiting on RPC response - topic: "network", RPC method: "allocate_for_instance" info: "<unknown>"\n']