Explicitly fail when there are unexpected arguments #942
Description
Most elastic-package subcommands are configured using flags, and they don't expect additional arguments. Currently additional arguments are ignored, what leads to confusion on certain use cases.
For example in #941, separating the services of the --services flags with spaces instead of commas leads to ignoring all the services except the first one.
elastic-package should fail when unexpected additional arguments are received to avoid having parameters silently ignored. Maybe showing the help text.