ensure-zookeeper: add use_tmpfs parameter

This change enables using the ensure-zookeeper role in environments
where mounting a filesystem is not allowed.

Change-Id: I1a05a895a45896eca91dccfcfc85aeb1a58689ff

roles/ensure-zookeeper/README.rst

@@ -13,3 +13,8 @@ Install and start zookeeper using the upsteam release.
    :default: false
 
    Setup zookeeper tls certificates.
+
+.. zuul:rolevar:: zookeeper_use_tmpfs
+   :default: true
+
+   Setup a tmpfs for data directory.

roles/ensure-zookeeper/defaults/main.yaml

@@ -3,4 +3,5 @@ _zookeeper_latest_version: "3.6.1"
 _zookeeper_install_version: "{% if zookeeper_version == 'latest' %}{{ _zookeeper_latest_version }}{% else %}{{ zookeeper_version }}{% endif %}"
 
 zookeeper_use_tls: false
+zookeeper_use_tmpfs: true
 zookeeper_ca_dir: "/opt/zookeeper/ca"

roles/ensure-zookeeper/tasks/main.yaml

@@ -35,6 +35,7 @@
     fstype: tmpfs
     opts: "nodev,nosuid,size=500M"
     src: "none"
+  when: zookeeper_use_tmpfs
   become: true
 
 - name: Setup Zookeeper config file