ecb73fd555 introduced a new keepVmState
CLI flag for test-driver.py. This CLI flags gets forwarded to the
Machine class through create_machine.
It created a regression for the boot tests where __main__ end up not
being evaluated. See
https://github.com/NixOS/nixpkgs/pull/97346#issuecomment-690951837 for
bug report.
Defaulting keepVmState to false when __main__ ends up not being
evaluated.
e571b315e2