[iam] try to fix flaky test

starting test server after usage_test.go

Author: AlexTugarev

components/iam/pkg/apiv1/oidc_config_test.go

@@ -119,9 +119,7 @@ func setupOIDCClientConfigService(t *testing.T) (v1.OIDCServiceClient, *gorm.DB)
 		require.NoError(t, srv.Close())
 	})
 
-	go func(t *testing.T) {
-		require.NoError(t, srv.ListenAndServe())
-	}(t)
+	baseserver.StartServerForTests(t, srv)
 
 	conn, err := grpc.Dial(srv.GRPCAddress(), grpc.WithTransportCredentials(insecure.NewCredentials()))
 	require.NoError(t, err)