Update README to use Docker image used in CI.

Fix local test reproduction broken by unsafe code.

Revert "Fix local test reproduction broken by unsafe code."

This reverts commit 7f98825.

Update README to use Docker image used in CI.

Author: niting

README.md

@@ -38,10 +38,10 @@ docker run --device=/dev/kvm \
            -it \
            --security-opt seccomp=unconfined \
            --volume $(pwd)/kvm-ioctls:/kvm-ioctls \
-           rustvmm/dev:v2
+           rustvmm/dev:v5
 cd kvm-ioctls/
 cargo test
 ```
 
 For more details about the integration tests that are run for `kvm-ioctls`,
-check the [rust-vmm-ci](https://github.com/rust-vmm/rust-vmm-ci) readme.
+check the [rust-vmm-ci](https://github.com/rust-vmm/rust-vmm-ci) readme.