use become: yes when root is needed

tasks/elasticsearch-optional-user.yml

@@ -1,6 +1,7 @@
 ---
 #Add the elasticsearch user before installing from packages.
 - name: Ensure optional elasticsearch group is created with the correct id.
+  become: yes
   group:
     state: present
     name: "{{ es_group }}"
@@ -8,6 +9,7 @@
     gid: "{{ es_group_id }}"
 
 - name: Ensure optional elasticsearch user is created with the correct id.
+  become: yes
   user:
     state: present
     name: "{{ es_user }}"