allowing job submission from EOS

The solution applied here is a mix of these two pages:

• https://batchdocs.web.cern.ch/troubleshooting/eos.html
• https://batchdocs.web.cern.ch/local/file_xfer_plugin.html

To run on EOS, the only prerequisite is to activate kerberos. Ideally, we should check that it was done and gently crash in case it was not, as users as likely to forget it (and the error message is not trivial to find nor to read).

It is no longer necessary to use condor_transfer_data.