Downgrade scheduler to Zuul 4.1.0

We found a bug in master which will prevent us from merging a fix;
downgrade the scheduler to 4.1.0 to get that in.

Change-Id: Ie9ad75177ab58b34e20cafab496ba7af6f082551

playbooks/roles/zuul-scheduler/files/docker-compose.yaml

@@ -5,7 +5,7 @@ version: '2'
 services:
   scheduler:
     restart: always
-    image: docker.io/zuul/zuul-scheduler:latest
+    image: docker.io/zuul/zuul-scheduler:4.1.0
     network_mode: host
     user: zuul
     volumes: