Replace deprecated os_adm

It was deprecated in tempest 16.1.0[1] in favor of os_admin.

[1] 8160d31e58eab90fde1f3412dae1099653482cc4

Change-Id: Ia5fab50e683c3c414401b635c30ce64b2ede5f6d
diff --git a/tempest/scenario/test_network_qos_placement.py b/tempest/scenario/test_network_qos_placement.py
index dbbc314..055dcb6 100644
--- a/tempest/scenario/test_network_qos_placement.py
+++ b/tempest/scenario/test_network_qos_placement.py
@@ -67,10 +67,10 @@
         cls.networks_client = cls.os_admin.networks_client
         cls.subnets_client = cls.os_admin.subnets_client
         cls.ports_client = cls.os_primary.ports_client
-        cls.routers_client = cls.os_adm.routers_client
+        cls.routers_client = cls.os_admin.routers_client
         cls.qos_client = cls.os_admin.qos_client
         cls.qos_min_bw_client = cls.os_admin.qos_min_bw_client
-        cls.flavors_client = cls.os_adm.flavors_client
+        cls.flavors_client = cls.os_admin.flavors_client
         cls.servers_client = cls.os_primary.servers_client
 
     def _create_flavor_to_resize_to(self):