mount: Run test_mount_bind in CI
mount: Run test_mount_bind in CI

Looks like Travis allows bind mounts in their container infra now.

kamalmarhubi/nix-rust,geofft/nix-rust,MarkusJais/nix-rust,xd009642/nix,kamalmarhubi/nix-rust,posborne/rust-nix,carllerche/nix-rust,xd009642/nix,posborne/rust-nix,Susurrus/nix,Susurrus/nix,asomers/nix,berkowski/nix,Susurrus/nix,geofft/nix-rust,posborne/rust-nix,carllerche/nix-rust,geofft/nix-rust,carllerche/nix-rust,MarkusJais/nix-rust,nix-rust/nix,berkowski/nix,asomers/nix,xd009642/nix,MarkusJais/nix-rust,kamalmarhubi/nix-rust,berkowski/nix,nix-rust/nix