playbooks: healthcheck-infrastructure: Ensure netcat is installed

The netcat package is required to perform the HAProxy tests so make
sure it is installed.

Change-Id: Ic2202164c224db6f24674f294a203f08165823fe

playbooks/healthcheck-infrastructure.yml

@@ -49,6 +49,10 @@
       changed_when: false
       when: groups['haproxy'] | length > 1
 
+    - package:
+        name: netcat
+        state: present
+
     # Fails if HAProxy is not running
     - name: Recording haproxy stats as a way to ensure haproxy runs
       shell: 'echo "show info;show stat" | nc -U /var/run/haproxy.stat'