The allManagementSubCommands function is used to present plugin-commands
in the docker --help output; these commands are included in the "management
commands" section, but for plugins we don't know if they have sub-commands.
However, plugin stubs may be hidden (for placeholders that are not yet loaded),
or not be runnable, which was previously ignored.
This patch treats plugin-stubs the same as other commands, with the exception
of checking if they have subcommands (which is not yet known for plugin-stubs).
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
259df25a96