adds test for 'rustup toolchain list' displaying default
adds test for 'rustup toolchain list' displaying default

nodakai/rustup.rs,nodakai/rustup.rs,nodakai/rustup.rs,rust-lang/rustup,polonez/rustup.rs,Boddlnagg/rustup.rs,theindigamer/rustup.rs,Boddlnagg/rustup.rs,nodakai/rustup.rs,theindigamer/rustup.rs,inejge/rustup.rs,nodakai/rustup.rs,polonez/rustup.rs,theindigamer/rustup.rs,theindigamer/rustup.rs,polonez/rustup.rs,polonez/rustup.rs,rust-lang/rustup,inejge/rustup.rs,inejge/rustup.rs,Boddlnagg/rustup.rs,inejge/rustup.rs,Boddlnagg/rustup.rs,Boddlnagg/rustup.rs,rust-lang/rustup,rust-lang/rustup,rust-lang/rustup,polonez/rustup.rs,inejge/rustup.rs,theindigamer/rustup.rs