Add custom systemd unit for Zookeeper

We're 100% systemd here, and the lack of control/information that the
old-school ZK initscript provides is frustrating. Replace it with our
own simple unit file.

roles/pvc/tasks/zookeeper/main.yml

@@ -2,7 +2,7 @@
 - name: install zookeeper packages
   apt:
     name:
-      - zookeeperd
+      - zookeeper
       - zookeeper-bin
     state: latest
 
@@ -18,7 +18,17 @@
     - zoo.cfg
   notify: restart zookeeper
 
-- name: start but disable services
+- name: install systemd unit file
+  template:
+    src: zookeeper/zookeeper.service.j2
+    dest: /etc/systemd/system/zookeeper.service
+  register: systemd
+
+- name: reload systemd to apply changes
+  command: systemctl daemon-reload
+  when: systemd.changed
+
+- name: start but disable services (managed by PVC)
   service:
     name: "{{ item }}"
     state: started

roles/pvc/templates/zookeeper/zookeeper.service.j2

@@ -0,0 +1,23 @@
+# Zookeeper unit - replaces zookeeperd package/initscript
+# {{ ansible_managed }}
+
+[Unit]
+Description = Zookeeper centralized coordination service
+After = remote-fs.target network.target
+AssertPathExists = /var/lib/zookeeper
+
+[Service]
+Type = simple
+User = zookeeper
+Group = zookeeper
+EnvironmentFile = -/etc/zookeeper/conf/environment
+EnvironmentFile = -/etc/default/zookeeper
+ExecStart = /usr/bin/java \
+              -cp $CLASSPATH \
+              $JAVA_OPTS \
+              -Dzookeeper.log.dir=${ZOO_LOG_DIR} \
+              -Dzookeeper.root.logger=${ZOO_LOG4J_PROP} \
+              $ZOOMAIN $ZOOCFG
+
+[Install]
+WantedBy = multi-user.target