Require TLS

Require TLS Zookeeper connections before making the 4.0 release.

Change-Id: I69acdcec0deddfdd191f094f13627ec1618142af
Depends-On: https://review.opendev.org/776696

nodepool/tests/fixtures/static-update.yaml

@@ -3,6 +3,11 @@ zookeeper-servers:
     port: {zookeeper_port}
     chroot: {zookeeper_chroot}
 
+zookeeper-tls:
+  ca: {zookeeper_ca}
+  cert: {zookeeper_cert}
+  key: {zookeeper_key}
+
 labels:
   - name: fake-label
   - name: fake-label2