Use only unique backends to iterate over

Prior output was containing same host multiple times. Applying uniq
to the stdout should eliminate that and result in running module only
once per host as was originally intended.

Change-Id: I0993a276d26a7da86fa60b8735de05ee24160395

ansible_tools/playbooks/set-haproxy-backends-state.yml

@@ -26,11 +26,11 @@
     - backend_state: enabled
   tasks:
     - name: List HAProxy backends to process
-      shell: echo show servers state | nc -U /var/run/haproxy.stat | awk '{print $4}' | grep '^{{ hostname }}'
+      ansible.builtin.shell: echo show servers state | nc -U /var/run/haproxy.stat | awk '{print $4}' | grep '^{{ hostname }}' | sort | uniq
       register: backends
       changed_when: false
     - name: Loop through backends to set state
-      haproxy:
+      community.general.haproxy:
         host: "{{ item }}"
         state: "{{ backend_state }}"
         socket: /var/run/haproxy.stat