scan_retention.py doesn't remove *pooled* files

[derpadoo]

Something like

target_files = set()
complete_dir_scans = set()
processed_dir_scans = set()
cancelled_dir_scans = set()
bigdata_analytics_dir_csv_files = set()

for file_base_name in [scan.result_file_base_name, scan.pooled_scan_result_file_base_name]:

    # Grab a list of files from the "target_files" directory.  Will capture any .excluded_targets as well.
    target_files.add(glob.glob(os.path.join(target_files_dir, f"{file_base_name}.*targets")))

    # Grab a list of files from the "complete" directory.
    complete_dir_scans.add(glob.glob(os.path.join(complete_dir, f"{file_base_name}*")))

    # Grab a list of files from the "processed" directory.
    processed_dir_scans.add(glob.glob(os.path.join(processed_dir, f"{file_base_name}*")))

    # Grab a list of files from the "cancelled" directory.
    cancelled_dir_scans.add(glob.glob(os.path.join(cancelled_dir, f"{file_base_name}*")))

    # Grab a list of .csv files from the "for_bigdata_analytics" directory.
    bigdata_analytics_dir_csv_files.add(glob.glob(
        os.path.join(bigdata_analytics_dir, f"{file_base_name}.csv")
    ))