Added parametrization of workers.

Change-Id: I657f405843b944ae88bd1bb95b4efbeebacde12f
diff --git a/metadata/service/control/single.yml b/metadata/service/control/single.yml
index 917a4ce..af1dc11 100644
--- a/metadata/service/control/single.yml
+++ b/metadata/service/control/single.yml
@@ -7,6 +7,7 @@
     server:
       enabled: true
       version: ${_param:glance_version}
+      workers: 1
       database:
         engine: mysql
         host: localhost