ligolw_segments_from_cats_dqsegdb deletes columns from Process table

@brennanhughey has discovered that the ligolw_segments_from_cats_dqsegdb executable is deleting valid columns from the Process table definition before reading a veto definer file, making it impossible to read files contain in those (valid) columns. The offending lines are here:

if __name__ == '__main__':
    # Settings
    del lsctables.ProcessTable.validcolumns['domain']
    del lsctables.ProcessTable.validcolumns['jobid']
    del lsctables.ProcessTable.validcolumns['is_online']

These are likely a hold-over from copying the old ligolw_segments_from_cats executable, in which these statements were removed nearly a year ago.

Can these lines be removed so that valid columns can be read?