[RTADPA BW Tests] Use new exp24 minbias for AllenInMoore_Hlt1_Bandwidth test

Standalone, is required by: lhcb-datapkg/PRConfig!358 (merged)

Updates Hlt1Conf/tests/options/bandwidth option files from the previous 'stand-in' input to the exp24 minbias.
Changes download_mdfs to instead be a wrapper of download_files, to allow addition of download_digis with little/no duplication.

Pending developments in PRConfig, this is ready.

Hlt/Moore/python/Moore/qmtest/context.py

@@ -168,7 +168,7 @@ def download_digi_inputs_locally(urls, dest_dir, max_size=None):
         assertion_endswith=assertion_endswith)
 
 
-def download_mdf_inputs_locally(urls, dest_dir, max_size):
+def download_mdf_inputs_locally(urls, dest_dir, max_size=None):
     """
     Calls download_inputs_locally specifically for mdf, mep or raw files.
     """