Use create_test_server wrapper for server creation

Since this wrapper responsible for server deletion we can
remove this action from the testcase.

Change-Id: I9878bd623f5ecefb0551136e41af2a4e15d1d5f6
diff --git a/tempest/api/compute/admin/test_auto_allocate_network.py b/tempest/api/compute/admin/test_auto_allocate_network.py
index c4d5768..e8011a6 100644
--- a/tempest/api/compute/admin/test_auto_allocate_network.py
+++ b/tempest/api/compute/admin/test_auto_allocate_network.py
@@ -148,9 +148,7 @@
     def test_server_create_no_allocate(self):
         """Tests that no networking is allocated for the server."""
         # create the server with no networking
-        server, _ = compute.create_test_server(
-            self.os_primary, networks='none', wait_until='ACTIVE')
-        self.addCleanup(self.delete_server, server['id'])
+        server = self.create_test_server(networks='none', wait_until='ACTIVE')
         # get the server ips
         addresses = self.servers_client.list_addresses(
             server['id'])['addresses']