Failure of attempting to delete a container that is not stopped

[dongsupark]

This is basically the same issue as the comment by @liangchenye.

According to the runtime spec, kill should be done by users before delete. However, runc delete actually implicitly kills the container. This is probably the reason why validation/delete.t in runtime-tools fails with an error message like

not ok 2 - attempting to delete a container that is not stopped MUST generate an error
{
  "reference": "https://github.com/opencontainers/runtime-spec/blob/v1.0.0/runtime.md#delete"
}

See also opencontainers/runtime-spec#958.