common: enable sending local logs to journald

common: enable sending local logs to journald

Enable ceph daemons to directly send logs to journald via unix domain socket.

While sending logs, metadata like priority, thread, timestamp is sent as
structured data. And can be queried by journalctl.

Note that I don't use libsystemd because I want the implementation to be as
efficient as possible.

Signed-off-by: 胡玮文 <huww98@outlook.com>