make possible to run validation tests in parallel

[belforte]

in the new CI pipeline based on GitLab runner, we have hit the situation where two scripts run at same time creating races in accessing ~/.crab3 cache file.

Should modify test script so that every crab command explicitly uses -d <directory> option.
And also point CRAB3_CRAB_CACHE to /dev/null to avoid possible access conflicts, see dmwm/CRABClient#5337

• add a remakeTask{} to https://github.com/dmwm/CRABServer/blob/v3.241018/test/testUtils.py (basically the first lines of current checkStatus{} : do a crab remake and returns directory name
• call it in https://github.com/dmwm/CRABServer/blob/v3.241018/test/makeTests.py so to explicitly pass -d ... to each command.
• remove the now duplicated code from checkStatus{}

That will allow running CCV in parallel with other tests.
CV is not straightforward, since having -d option or not should ideally part of the test itself.

It looks to me that ST test is safe on this regard. But should be reviewed.