Noble 24.04 minor improvements

[hector-cao]

This PR comes with 2 commits:

• output the qemu command to a script
  this will allow users to run manually the guest after the test
  this capability is useful for debugging purposes
  for example, the user can run the guest manually by doing:

$ sudo /tmp/tdxtest-default-hk8u6mf3/run.sh

hk8u6mf3 is random and may vary for each test

• right now, we use proc.terminate() to send SIGTERM to qemu process
  this tends to corrupt the rootfs
  this will prevent us from running the guest again with this rootfs
  try to stop the VM (shutdown) properly first and terminate() it
  later if necessary

[frenchwr]

LGTM. Only thing I'm wondering is if you need or want to document how to use the qemu troubleshooting script, but I leave it up to you, so not a blocker.

[hector-cao]

LGTM. Only thing I'm wondering is if you need or want to document how to use the qemu troubleshooting script, but I leave it up to you, so not a blocker.

Yes, agree but i have the feeling that for now, i m the only one who runs the tests. but definitely if someone starts to use them, i can enrich the documentation