Revert "Revert "Temporarily stop booting nodes in inap-mtl01""

The previously observed problem (looks like rogue server instances
again) still appears to persist there.

This reverts commit 492e9eeba1.

Change-Id: I8c70268af93f4fe32a730834b405942602417a82

nodepool/nl03.openstack.org.yaml

@@ -100,7 +100,7 @@ providers:
         config-drive: true
     pools:
       - name: main
-        max-servers: 95
+        max-servers: 0
         labels:
           - name: centos-7
             min-ram: 8000