Comment 11 for bug 2056461

Latest findings:
* The deepest loop that actually never exits is actually the `while not os.path.exists(fexit):` in the `eofcat` script. This is because the `block = os.read(0, 1000000)` always reads nothing.
* From the guest:
  * `head`ing the `stdin` file doesn't help.
  * `tail`ing the `stdin` file does help, it unblocks the loop, just the same way as `stat`ing it.
* From the host:
  * `stat`ing `stdin` doesn't change anything.
  * Appending more data to it doesn't change anything either.
  * This adds up with the fact that it's a kernel change in the guest that triggered the bug.
* That `stdin` file is stored on a 9p shared FS. This might be a related change, but nothing confirmed yet: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c9b93cafb69cbbbe375de29c1ebf410dbc33ebfc