Revert "Disable nodepool temporarily"

This reverts commit 4f06690ce9.

Reason for revert: upgrade is done

Change-Id: Ie19d41c218ba266d6174e2ddf8571f393246e4f1

nodepool/nl04.opendev.org.yaml

@@ -78,7 +78,7 @@ providers:
         config-drive: true
     pools:
       - name: main
-        max-servers: 0
+        max-servers: 120
         labels: &provider_pools_labels
           - name: centos-7
             min-ram: 8000