This fix tries to fix 26326 where `docker inspect` will not show
ulimit even when daemon default ulimit has been set.
This fix merge the HostConfig's ulimit with daemon default in
`docker inspect`, so that when daemon is started with `default-ulimit`
and HostConfig's ulimit is not set, `docker inspect` will output
the daemon default.
An integration test has been added to cover the changes.
This fix fixes 26326.
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>
