Fix some tempest deprecation warnings

Saw this recently in a tempest test run:

    DeprecationWarning: Read-only property 'manager'
    has moved to 'os_primary' in version 'Pike' and
    will be removed in version 'Queens'

Tempest BaseTestCase class credential names have changed
from manager->os_primary, admin->os_admin, and
alt_manager->os_alt, so we should start using them.

Closes-bug: #1697588
Change-Id: I44de8046fc983bf6780c310e8db174a5902c2826
diff --git a/neutron/tests/tempest/scenario/test_trunk.py b/neutron/tests/tempest/scenario/test_trunk.py
index c857f3f..8ad9078 100644
--- a/neutron/tests/tempest/scenario/test_trunk.py
+++ b/neutron/tests/tempest/scenario/test_trunk.py
@@ -86,7 +86,7 @@
     def _detach_and_delete_trunk(self, server, trunk):
         # we have to detach the interface from the server before
         # the trunk can be deleted.
-        self.manager.compute.InterfacesClient().delete_interface(
+        self.os_primary.compute.InterfacesClient().delete_interface(
             server['id'], trunk['port_id'])
 
         def is_port_detached():
@@ -137,7 +137,7 @@
         }
 
     def _wait_for_server(self, server):
-        waiters.wait_for_server_status(self.manager.servers_client,
+        waiters.wait_for_server_status(self.os_primary.servers_client,
                                        server['server']['id'],
                                        constants.SERVER_STATUS_ACTIVE)
         self.check_connectivity(server['fip']['floating_ip_address'],