Merge fix-1680875-fix-packaging-conflicts [f=1680875] [r=free.ekanayaka,chad.smith,landscape-builder] [a=Eric Snow]
Factor out a common setup package for landscape-client and landscape-sysinfo.
This removes possible conflicts between the Python 2 and Python 3 lib packages.
Note that, as part of this change, the landscape-common packages have been
renamed to pythonX-landscape-lib.