Default etherpad_hostname to matrix_server_fqn_etherpad for backward compatibility

group_vars/matrix_servers

@@ -2222,6 +2222,8 @@ etherpad_base_path: "{{ matrix_base_data_path }}/etherpad"
 
 etherpad_framing_enabled: "{{ matrix_dimension_enabled or matrix_jitsi_enabled }}"
 
+etherpad_hostname: "{{ matrix_server_fqn_etherpad }}"
+
 etherpad_container_image_self_build: "{{ matrix_architecture not in ['amd64'] }}"
 
 etherpad_container_http_host_bind_port: "{{ (matrix_playbook_service_host_bind_interface_prefix ~ '9001') if matrix_playbook_service_host_bind_interface_prefix else '' }}"