Prepare for bin-sbin merge
    
    https://fedoraproject.org/wiki/Changes/Unify_bin_and_sbin
    
    - do not hardcode "/usr/sbin" in most places, use the macro instead.
    - fix build when %_sbindir==%_bindir.
    - add compat Provides for Requires in other packages. Rely on
      filesystem creating symlinks for us.
    
    This commit makes things compatible with the state before and after
    the merge.