定义：
cloudmgr_docker_log_options:
"syslog-address": "tcp://192.168.108.29:9700"
"syslog-facility": "daemon"
增加一对key-value：
- name: Set log tag
set_fact:
log_tag: { 'tag': '{{ cloudmgr_region_console.server.hostname }}' }
log_options: "{{ cloudmgr_docker_log_options | combine(log_tag) }}"
https://stackoverflow.com/questions/31772732/ansible-how-to-keep-appending-new-keys-to-a-dictionary-when-using-set-fact-mod
