client175: Convert python2 modules in source tarball to python3

client175: Convert python2 modules in source tarball to python3

- Patch created to convert all python modules to python3 compatibility that need it.
   2to3 converter used for this.
- Start initscript changed to use python3
- No change required in rootfile
- Execution of patch added to lfs file
- Tested in vm machine. WUI page showed the same as with the python version.
   scan of directory for mp3 (.flac) files was successful. Could not test actual audio
   playing capability as my vm testbed does not have any audio setup at this time.
  I believe that the purpose of client175 is to provide the WUI page and for that my
   testing seemed to show everything working as expected.

Tested-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Adolf Belka <adolf.belka@ipfire.org>
Signed-off-by: Arne Fitzenreiter <arne_f@ipfire.org>