Command nova-status upgrade check always return warning when checking resource providers

Description
===========
Version: master
Cluster model: 1 controller and 1 compute

I used nova api database for placement service.

When I run command: "nova-status upgrade check",
the output always warning in check resource providers.

Expected result
===============
+--------------------------------+
| Check: Resource Providers |
| Result: Success |
| Details: None |
+--------------------------------+

Actual result
=============
+-------------------------------------------------------------------+
| Check: Resource Providers |
| Result: Warning |
| Details: There are no compute resource providers in the Placement |
| service but there are 1 compute nodes in the deployment. |
| This means no compute nodes are reporting into the |
| Placement service and need to be upgraded and/or fixed. |
| See |
| https://docs.openstack.org/nova/latest/user/placement.html |
| for more details. |
+-------------------------------------------------------------------+

Logs & Configs
==============
I checked in nova-compute.log that compute node was reported to placement
service with log:
"INFO nova.compute.resource_tracker [req-52b91ba5-518c-476c-ad63-a2c83a1a43c3 - - - - -]
Compute node record created for compute1:compute1 with uuid ..."

The resource_providers table in nova_api database:

MariaDB [nova_api]> select * from resource_providers;
+---------------------+---------------------+----+--------------------------------------+----------+------------+----------+------------------+--------------------+
| created_at | updated_at | id | uuid | name | generation | can_host | root_provider_id | parent_provider_id |
+---------------------+---------------------+----+--------------------------------------+----------+------------+----------+------------------+--------------------+
| 2018-08-16 07:20:33 | 2018-08-27 03:12:37 | 1 | a5ac6e98-9935-456c-9de1-10f47adb81d6 | compute1 | 7 | NULL | 1 | NULL |
+---------------------+---------------------+----+--------------------------------------+----------+------------+----------+------------------+--------------------+