Bug 1462307

Description of problem:
Failed create several instances under REST API load test. 
Message:
"Remote error: DBAPIError (exceptions.RuntimeError) reentrant call inside <_io.BufferedReader name=5> [u'Traceback (most recent call last):\n', u' File "/usr/lib/python2.7/site-packages/oslo_messaging/rpc/server.py", line 155, in _process_incoming\n re"
Details:
"File "/usr/lib/python2.7/site-packages/nova/conductor/manager.py", line 866, in schedule_and_build_instances request_specs[0].to_legacy_filter_properties_dict()) File "/usr/lib/python2.7/site-packages/nova/conductor/manager.py", line 597, in _schedule_instances hosts = self.scheduler_client.select_destinations(context, spec_obj) File "/usr/lib/python2.7/site-packages/nova/scheduler/utils.py", line 371, in wrapped return func(*args, **kwargs) File "/usr/lib/python2.7/site-packages/nova/scheduler/client/__init__.py", line 51, in select_destinations return self.queryclient.select_destinations(context, spec_obj) File "/usr/lib/python2.7/site-packages/nova/scheduler/client/__init__.py", line 37, in __run_method return getattr(self.instance, __name)(*args, **kwargs) File "/usr/lib/python2.7/site-packages/nova/scheduler/client/query.py", line 32, in select_destinations return self.scheduler_rpcapi.select_destinations(context, spec_obj) File "/usr/lib/python2.7/site-packages/nova/scheduler/rpcapi.py", line 129, in select_destinations return cctxt.call(ctxt, 'select_destinations', **msg_args) File "/usr/lib/python2.7/site-packages/oslo_messaging/rpc/client.py", line 169, in call retry=self.retry) File "/usr/lib/python2.7/site-packages/oslo_messaging/transport.py", line 97, in _send timeout=timeout, retry=retry) File "/usr/lib/python2.7/site-packages/oslo_messaging/_drivers/amqpdriver.py", line 505, in send retry=retry) File "/usr/lib/python2.7/site-packages/oslo_messaging/_drivers/amqpdriver.py", line 496, in _send raise result"
nova-conductor.log has many errors (see attached file) 
Look for instance:
Name    perf-18-1-vm
ID    d967103b-8866-4e29-823a-8bfadd748d85
Status    Error
Created    June 15, 2017, 9:11 p.m.

Version-Release number of selected component (if applicable):
rhos-release 11   -p 2017-05-30.1
[root@overcloud-controller-0 log]# rpm -qa | grep nova
openstack-nova-novncproxy-15.0.3-3.el7ost.noarch
python-nova-15.0.3-3.el7ost.noarch
openstack-nova-cert-15.0.3-3.el7ost.noarch
openstack-nova-migration-15.0.3-3.el7ost.noarch
openstack-nova-api-15.0.3-3.el7ost.noarch
python-novaclient-7.1.0-1.el7ost.noarch
puppet-nova-10.4.0-5.el7ost.noarch
openstack-nova-compute-15.0.3-3.el7ost.noarch
openstack-nova-scheduler-15.0.3-3.el7ost.noarch
openstack-nova-console-15.0.3-3.el7ost.noarch
openstack-nova-common-15.0.3-3.el7ost.noarch
openstack-nova-conductor-15.0.3-3.el7ost.noarch
openstack-nova-placement-api-15.0.3-3.el7ost.noarch

How reproducible:
It could be reproduced by run the REST API performance test
which simulates load on Openstack with 20 concurrent threads.
Each thread create instance and perform actions:
01.NOVA.GET.Images
02.NOVA.GET.Flavors
03.NEUTRON.POST.Create.Network
04.NEUTRON.POST.Create.Subnet
05.NOVA.POST.Boot.Server
00.NOVA.GET.Server.Details
06.NOVA.POST.Pause.Server
07.NOVA.POST.Unpause.Server
08.NOVA.POST.Suspend.Server
09.NOVA.POST.Resume.Server
10.NOVA.POST.Soft.Reboot.Server
11.NOVA.POST.Hard.Reboot.Server
12.NOVA.POST.Stop.Server
13.NOVA.POST.Start.Server
14.NOVA.POST.Create.Image
15.NOVA.GET.Image.Id
16.NOVA.DELETE.Image
17.NOVA.DELETE.Server
18.NEUTRON.DELETE.Network

Steps to Reproduce:
1.
2.
3.

Actual results:
Several instances in state Error

Expected results:
No instances in state Error

Additional info:
Not happened in RHOS 9 and 10