Update cobbler to rev 54 via SR 792600
    
    https://build.opensuse.org/request/show/792600
    by user trenn + dimstar_suse
    - Removed not needed files in obs. This is now all mainline:
    D logrotate_cobbler
    D fix_hardcoded_libpath_for_websession.patch
    D fence_ipmitool.template
    D cobbler_management_mac.diff
    D AUTHORS
    - Added source files:
    A cobbler.obsinfo
    A cobbler-rpmlintrc
    D exclude_get-loaders_command.patch
    Spec file is mostly adopted to mainline spec file.
    Still it is not directly extracted from mainline tarball.
    First the remaining diff has to be submitted mainline.
    - Change group to Productivity/Networking/Boot/Servers
    - Disable any python_*_dependency_generator macros
      According to Tomas Chvatal they are much too experimental yet
      in OBS to be used. They have to be undefined, because of a half
      baken implementation in SLE 15 SP2 build env (defined but not
      properly implemented). At some point of time th