This fix tries to address the issue raised in 25696 where
it was not possible to specify `--stop-signal` for `docker service create`
and `docker service update`, in order to use special signal to stop
the container.
This fix adds `--stop-signal` and update the `StopSignal` in `Config`
through `service create` and `service update`.
Related docs has been updated.
Integration test has been added.
This fix fixes 25696.
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>
Upstream-commit: c2d49ec214649b0025f7060429334893350fbaee
Component: engine
5050030ffa