Start minimally using Open Edge environment

The new Open Edge provider, replacing Fortnebula, is likely ready
for workloads. Start with a maximum of one for each of its main and
custom pools to make sure things are working as expected before we
try to increase load there.

Change-Id: I5578881d52f56dfeb5c5254bfa417c90fa27ebe5

nodepool/nl02.openstack.org.yaml

@@ -261,10 +261,10 @@ providers:
     boot-timeout: 120
     launch-timeout: 300
     rate: 0.01
-    diskimages: []
+    diskimages: *provider_diskimages
     pools:
       - name: main
-        max-servers: 0
+        max-servers: 1
         labels:
           - name: centos-7
             min-ram: 8000
@@ -332,7 +332,7 @@ providers:
             diskimage: centos-7
             key-name: infra-root-keys-2018-06-15
       - name: custom
-        max-servers: 0
+        max-servers: 1
         labels:
           - name: centos-7-expanded
             min-ram: 16000