tests: Retry failed cases automatically in parallel VM run

parallel-vm.py is now retrying failed cases once at the end of the run.
If all the failed test cases passed on the second attempt, that is noted
in the summary output. Results are also indicated as the exit value from
the run: 0 = all cases passed on first run, 1 = some cases failed once,
but everything passed after one retry, 2 = some cases failed did not
succeed at all.

Signed-off-by: Jouni Malinen <j@w1.fi>
1 file changed