MuonIdentification: cmake and flake8 fixes

Enable flake8 and make code compliant for three MuonIdentification packages. Also apply some minor cmake fixes.

Reconstruction/MuonIdentification/MuonCombinedAlgs/python/MuonCombinedAlgsMonitoring.py

+# Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
 # Author: Laurynas Mince
 # Created on 26.07.2019