Tempest allow_tenant_isolation in auth section

Tempest change 107685 moves allow_tenant_isolation from compute
group to auth group, making the old format deprecated.
Switching to the new format.

Change-Id: Iff79986c2564610efde4791b7e61df3db859e199
diff --git a/lib/tempest b/lib/tempest
index d6d6020..4fc064c 100644
--- a/lib/tempest
+++ b/lib/tempest
@@ -272,8 +272,10 @@
         iniset $TEMPEST_CONFIG image http_image $TEMPEST_HTTP_IMAGE
     fi
 
+    # Auth
+    iniset $TEMPEST_CONFIG auth allow_tenant_isolation ${TEMPEST_ALLOW_TENANT_ISOLATION:-True}
+
     # Compute
-    iniset $TEMPEST_CONFIG compute allow_tenant_isolation ${TEMPEST_ALLOW_TENANT_ISOLATION:-True}
     iniset $TEMPEST_CONFIG compute ssh_user ${DEFAULT_INSTANCE_USER:-cirros} # DEPRECATED
     iniset $TEMPEST_CONFIG compute network_for_ssh $PRIVATE_NETWORK_NAME
     iniset $TEMPEST_CONFIG compute ip_version_for_ssh 4