Return error for incorrect argument of `service update --publish-rm <TargetPort>`

Currently `--publish-rm` only accepts `<TargetPort>` or `<TargetPort>[/Protocol]`
though there are some confusions.

Since `--publish-add` accepts `<PublishedPort>:<TargetPort>[/Protocol]`, some user
may provide `--publish-rm 80:80`. However, there is no error checking so the incorrect
provided argument is ignored silently.

This fix adds the check to make sure `--publish-rm` only accepts `<TargetPort>[/Protocol]`
and returns error if the format is invalid.

The `--publish-rm` itself may needs to be revisited to have a better UI/UX experience,
see discussions on:
https://github.com/docker/swarmkit/issues/1396
https://github.com/docker/docker/issues/25200#issuecomment-236213242
https://github.com/docker/docker/issues/25338#issuecomment-240787002

This fix is short term measure so that end users are not misled by the silently ignored error
of `--publish-rm`.

This fix is related to (but is not a complete fix):
https://github.com/docker/swarmkit/issues/1396

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

opts/opts.go

@@ -108,6 +108,12 @@ func (opts *ListOpts) Type() string {
 	return "list"
 }
 
+// WithValidator returns the ListOpts with validator set.
+func (opts *ListOpts) WithValidator(validator ValidatorFctType) *ListOpts {
+	opts.validator = validator
+	return opts
+}
+
 // NamedOption is an interface that list and map options
 // with names implement.
 type NamedOption interface {