Enabling the reading of N and M value from the json request

For this commit only the first element from the {N, M} list is read
and assigned.

This is better than not reading this value at all.

the commit also updates test_files and test data files with correct
values for the effective_freq_slot attribute

Signed-off-by: EstherLerouzic <esther.lerouzic@orange.com>
Change-Id: I1e60fe833ca1092b40de27c8cbfb13083810414e

tests/test_parser.py

@@ -394,6 +394,7 @@ def test_excel_ila_constraints(source, destination, route_list, hoptype, expecte
         'nb_channel': 0,
         'power': 0,
         'path_bandwidth': 0,
+        'effective_freq_slot': None
     }
     request = PathRequest(**params)