Disable OVH BHS1 region

This reverts commit 756a8f43f7c5458fb7b4c831e6c1ef65918dc6f6, which
was where we re-enabled OVH BHS1 after maintenance.  I strongly
suspect that this has something to do with the issues ...

It appears that VM's in BHS1 can not communicate with the mirror

From a sample host 158.69.64.62 to mirror01.bhs1.ovh.openstack.org

---
 root@ubuntu-bionic-ovh-bhs1-0002154210:~# ip addr
 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
 2: ens3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether fa:16:3e:1b:4b:32 brd ff:ff:ff:ff:ff:ff
    inet 158.69.64.62/19 brd 158.69.95.255 scope global ens3
       valid_lft forever preferred_lft forever
    inet6 fe80::f816:3eff:fe1b:4b32/64 scope link
       valid_lft forever preferred_lft forever

 root@ubuntu-bionic-ovh-bhs1-0002154210:~# traceroute -n mirror01.bhs1.ovh.openstack.org
 traceroute to mirror01.bhs1.ovh.openstack.org (158.69.80.87), 30 hops max, 60 byte packets
  1  158.69.64.62  2140.650 ms !H  2140.627 ms !H  2140.615 ms !H

 root@ubuntu-bionic-ovh-bhs1-0002154210:~# ping mirror01.bhs1.ovh.openstack.org
 PING mirror01.bhs1.ovh.openstack.org (158.69.80.87) 56(84) bytes of data.
 From ubuntu-bionic-ovh-bhs1-0002154210 (158.69.64.62) icmp_seq=1 Destination Host Unreachable
 From ubuntu-bionic-ovh-bhs1-0002154210 (158.69.64.62) icmp_seq=2 Destination Host Unreachable
 From ubuntu-bionic-ovh-bhs1-0002154210 (158.69.64.62) icmp_seq=3 Destination Host Unreachable
 --- mirror01.bhs1.ovh.openstack.org ping statistics ---
 4 packets transmitted, 0 received, +3 errors, 100% packet loss, time 3049ms
---

However, *external* access to the mirror host and all other hosts
seems fine.  It appears to be an internal OVH BHS1 networking issue.

I have raised ticket #9721374795 with OVH about this issue.  It needs
to be escalated so is currently pending (further details should come
to infra-root@openstack.org).

In the mean time, all jobs are failing in the region.  Disable it
until we have a solution.

Change-Id: I748ca1c10d98cc2d7acf2e1821d4d0f886db86eb

nodepool/nl04.openstack.org.yaml

@@ -50,7 +50,7 @@ providers:
         config-drive: true
     pools:
       - name: main
-        max-servers: 159
+        max-servers: 0
         labels: &provider_pools_labels
           - name: centos-7
             min-ram: 8000