Add tests of port_id in the attach interfaces nova API

The attach interfaces API of nova does not specify port_id or
fixed_ips in tempests.
So, need to check these behavior in tempests.

This patch include test case of port_id.

Change-Id: I9f69c267fdf63126e93f334c988fda77464ca2b0
Closes-bug: #1525813
diff --git a/tempest/api/compute/servers/test_attach_interfaces.py b/tempest/api/compute/servers/test_attach_interfaces.py
index 24d503f..be79163 100644
--- a/tempest/api/compute/servers/test_attach_interfaces.py
+++ b/tempest/api/compute/servers/test_attach_interfaces.py
@@ -45,9 +45,10 @@
     def setup_clients(cls):
         super(AttachInterfacesTestJSON, cls).setup_clients()
         cls.client = cls.os.interfaces_client
+        cls.ports_client = cls.os.ports_client
 
     def wait_for_interface_status(self, server, port_id, status):
-        """Waits for a interface to reach a given status."""
+        """Waits for an interface to reach a given status."""
         body = (self.client.show_interface(server, port_id)
                 ['interfaceAttachment'])
         interface_status = body['port_state']
@@ -108,6 +109,18 @@
         self._check_interface(iface, network_id=network_id)
         return iface
 
+    def _test_create_interface_by_port_id(self, server, ifs):
+        network_id = ifs[0]['net_id']
+        port = self.ports_client.create_port(network_id=network_id)
+        port_id = port['port']['id']
+        self.addCleanup(self.ports_client.delete_port, port_id)
+        iface = self.client.create_interface(
+            server['id'], port_id=port_id)['interfaceAttachment']
+        iface = self.wait_for_interface_status(
+            server['id'], iface['port_id'], 'ACTIVE')
+        self._check_interface(iface, port_id=port_id)
+        return iface
+
     def _test_show_interface(self, server, ifs):
         iface = ifs[0]
         _iface = self.client.show_interface(
@@ -167,6 +180,9 @@
         iface = self._test_create_interface_by_network_id(server, ifs)
         ifs.append(iface)
 
+        iface = self._test_create_interface_by_port_id(server, ifs)
+        ifs.append(iface)
+
         _ifs = (self.client.list_interfaces(server['id'])
                 ['interfaceAttachments'])
         self._compare_iface_list(ifs, _ifs)