Start instances using fixed network when possible

Uses the fixed_network_name option to select which network
to boot test instances on.  This allows Tempest to be run
in environments where there are multiple networks available.

This problem does not apply to nova-network environments because
it will happily start instances with multiple networks attached,
so the behavior is left as before in that case.

Co-Authored-By: Ben Nemec <bnemec@redhat.com>
Co-Authored-By: Vincent Untz <vuntz@suse.com>
Co-Authored-By: git-harry <git-harry@live.co.uk>

Change-Id: Ib5b84b59e3d182d8b9cc83954537c32f3eb9e388
Closes-Bug: #1250866
diff --git a/tempest/api/compute/admin/test_servers.py b/tempest/api/compute/admin/test_servers.py
index c872184..ef3a029 100644
--- a/tempest/api/compute/admin/test_servers.py
+++ b/tempest/api/compute/admin/test_servers.py
@@ -16,6 +16,7 @@
 from tempest_lib import decorators
 
 from tempest.api.compute import base
+from tempest.common import fixed_network
 from tempest import test
 
 
@@ -112,7 +113,10 @@
         name = data_utils.rand_name('server')
         flavor = self.flavor_ref
         image_id = self.image_ref
-        test_server = self.client.create_server(name, image_id, flavor)
+        network = self.get_tenant_network()
+        network_kwargs = fixed_network.set_networks_kwarg(network)
+        test_server = self.client.create_server(name, image_id, flavor,
+                                                **network_kwargs)
         self.addCleanup(self.client.delete_server, test_server['id'])
         self.client.wait_for_server_status(test_server['id'], 'ACTIVE')
         server = self.client.get_server(test_server['id'])