Consolidate install smoke tests
Consolidate install smoke tests

These three smoke tests are not interestingly different: they lose
nothing by being a single test, but we gain by less time in serialised
tests.

rust-lang/rustup,nodakai/rustup.rs,nodakai/rustup.rs,rust-lang/rustup,nodakai/rustup.rs,nodakai/rustup.rs,rust-lang/rustup,rust-lang/rustup,nodakai/rustup.rs,rust-lang/rustup