Disable infracloud

We are seeing large numbers of ssh failures to infracloud test nodes.
Let's disable the cloud while we work through other issues in the zuulv3
transition.

Change-Id: I6107154efb56de876c63b6c587072f5001b141ef

nodepool/nl02.openstack.org.yaml

@@ -260,7 +260,7 @@ providers:
         config-drive: true
     pools:
       - name: main
-        max-servers: 56
+        max-servers: 0
         labels:
           - name: centos-7
             min-ram: 8000
@@ -313,7 +313,7 @@ providers:
         config-drive: true
     pools:
       - name: main
-        max-servers: 56
+        max-servers: 0
         labels:
           - name: centos-7
             min-ram: 8000