This fix tries to address an issue raised in #24090 where
the title field of `docker node ls` use NAME instead of
HOSTNAME. Yet the content of this field is actually
hostname.
The fix makes needed changes for the output of
`docker node ls`.
An additional test has been added to cover the change in
this fix.
This fix fixes#24090.
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>
