Replace the usage of 'admin_manager' with 'os_admin'

In tempest, alias 'admin_manager' has been moved to 'os_admin'
'alt_manager' to 'os_alt' and 'manager' to 'os_primary' in
version Pike, and it will be removed in version Queens[1].


[1]I5f7164f7a7ec5d4380ca22885000caa0183a0bf7

Closes-bug: 1697588

Change-Id: Ib41a1bcff70cc7323b90a222c9f64d66e0203e53
diff --git a/neutron/tests/tempest/api/test_qos.py b/neutron/tests/tempest/api/test_qos.py
index 0a9bcda..f35abd8 100644
--- a/neutron/tests/tempest/api/test_qos.py
+++ b/neutron/tests/tempest/api/test_qos.py
@@ -561,7 +561,7 @@
     @classmethod
     def resource_setup(cls):
         super(RbacSharedQosPoliciesTest, cls).resource_setup()
-        cls.client2 = cls.alt_manager.network_client
+        cls.client2 = cls.os_alt.network_client
 
     def _create_qos_policy(self, tenant_id=None):
         args = {'name': data_utils.rand_name('test-policy'),