Auto merge of #5209 - matklad:no-way-we-havent-had-a-test-for-this, r=alexcrichton

Fix regression when passing arguments to subcommands

closes https://github.com/rust-lang/cargo/issues/5208

`.args(&args[1..])` was copied directly from the docopt implementation, but there, `args[0]` was the path to `cargo` and not the name of subcommand, ie, `args` were *original* arguments for Cargo as a whole.