Allow CI to run with external LHE inputs

The CI can currently not yet run jobs with input event files. Largely the same tasks appear for both LHE->EVNT and EVNT->EVNT files:

• Upload mcgensvc grid certificate in CI and make sure voms-proxy-init -voms atlas works in the CI

• Write (rucio) file that was used in local testing into log.generate.short, e.g. inputGeneratorFile=TXT.<dsid>.tar.gz for LHE or inputEVNTFile=1231231.EVNT.pool.root for EVNT input.

• If input file is specified in log.generate.short, the CI run_athena.sh job should rucio get that file and add the corresponding arguments to the Gen_tf.py command line as described in Twiki.

• Special treatment for EVNT->EVNT jobs: Apparently such jobs do not produce a log.generate file but a log.afterburn. Disable logParser for these, or special treatment? (move to #139 (closed))

• Ideally, the CI should also check the inputFilesPerJob in the JO for reasonable values at this stage: it should not exceed 10GB/sizeof(downloadedTestFile) to make sure they fit into a grid node.

• Similar case that came up in #89 (closed) is running athena with --inputGeneratorFile

Example !203 (merged)

LHE-only log: ~sargyrop/public/log.generate_LHE