REGTEST: script: Add the option --clean to remove previous log direcotries

Running regtests several times leaves many direcotries. It is painful to remove
them by hand. This command do it for you. It ask a confirmation to proceed to be
sure. The template used to create log direcotries has been changed. The prefix
'haregtests-' has been added to help the cleanup function to find existing log
direcotries.
1 file changed