Build: fix distribution of daemons/ipa-slapi-plugins/topology files
    
    All the headers are now listed in _SOURCES variable.
    It seems weird but this is what GNU Automake manual suggests in section
    9.2 Header files:
      Headers used by programs or convenience libraries are not installed.
      The noinst_HEADERS variable can be used for such headers.
      However when the header actually belongs to a single convenience library
      or program, we recommend listing it in the program’s or library’s
      _SOURCES variable (see Program Sources) instead of in noinst_HEADERS.
      This is clearer for the Makefile.am reader.
      noinst_HEADERS would be the right variable to use in a directory containing
      only headers and no associated library or program.
    
    https://fedorahosted.org/freeipa/ticket/6418
    
    Reviewed-By: Martin Basti <mbasti@redhat.com>
    Reviewed-By: Christian Heimes <cheimes@redhat.com>