The security infomation has already been added to `GET /info` in #21172.
However, it is not part of the output of `docker info` yet.
This fix adds the security information to `docker info`.
Additional tests has been added to cover changes.
This fix fixes#23500. This fix is related to #20909, #21172.
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>
