Noticed few places where tests seem to block indefinitely and panic
after the test run reaches the test package timeout.
I intend to follow up with the proper fix later, but timing out is much
better than indefinitely blocking.
Using statically linked busybox binary to setup a basic rootfs for
testing, by symlinking it to provide the basic commands used in tests.
I considered using a proper rootfs tarball, but the overhead of managing
tarfile and expanding it seems significant enough that I went with this
implementation.
Currently, libcontainer-based executor, upon shutdown, kills the
container initial process. The children of the killed process remain
running, and the executor is never marked as terminated until they do.
Also, fix a case where we treat processes as successful, when
`proc.Wait()` fails. In some attempts, I was getting "waitid no child
processes" errors and such error shouldn't get process to be considered
successful.
