Neutron test cases create,list,update port failed

while running test case over neutron plugin(contrail) with dpdk/sriov
computes, host_id in "binding:host_id" should be compute node name.so
that port can be allocated to a given compute host.

Here we are using "cls.host_id = socket.hostname()" which return
hostname of tempest host.Vrouter will looking for compute node
with tempest hostname to bind port there but didn't found any compute
node with tempest hostname.So raised an exception.

Details: {u'message': u'bad virtual_machine_interface request:
internal error: virtual router default-global-system-config:openstack
not found', u'type': u'badrequest', u'detail': u''}

To get test case running host_id should be compute node name.

Hyper_list = cls.hyper_client.list_hypervisors()
cls.host_id = hyper_list['hypervisors'][0]['hypervisor_hostname']

closes-bug: #1742096

Change-Id: I943150845fa05f24566ea0cd282306136688039b
diff --git a/tempest/api/network/admin/test_ports.py b/tempest/api/network/admin/test_ports.py
index 807994b..483b405 100644
--- a/tempest/api/network/admin/test_ports.py
+++ b/tempest/api/network/admin/test_ports.py
@@ -13,8 +13,6 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import socket
-
 from tempest.api.network import base
 from tempest import config
 from tempest.lib import decorators
@@ -25,10 +23,16 @@
 class PortsAdminExtendedAttrsTestJSON(base.BaseAdminNetworkTest):
 
     @classmethod
+    def setup_clients(cls):
+        super(PortsAdminExtendedAttrsTestJSON, cls).setup_clients()
+        cls.hyper_client = cls.os_admin.hypervisor_client
+
+    @classmethod
     def resource_setup(cls):
         super(PortsAdminExtendedAttrsTestJSON, cls).resource_setup()
         cls.network = cls.create_network()
-        cls.host_id = socket.gethostname()
+        hyper_list = cls.hyper_client.list_hypervisors()
+        cls.host_id = hyper_list['hypervisors'][0]['hypervisor_hostname']
 
     @decorators.idempotent_id('8e8569c1-9ac7-44db-8bc1-f5fb2814f29b')
     def test_create_port_binding_ext_attr(self):