- When container is not running, the runtime helper
traverses the container's root fs and writes it to the
specified tar archive or stdout.
- When the container is running, the helper performs
the same operation but wraps it in freeze/thaw
to ensure data integrity for the resulting archive.
Today when we send a signal we don't wait for the container to exit, as
we don't know what signals the program will actually do anything with.
However, sigkill does not fit this mold, and we should wait for the
container to exit (or be removed for --rm containers).