don't pull libreport-python with libreport
setroubleshoot and python-meh (anaconda) have libreport-python in their
Requires, so there is no need to have libreport-python in Requires of
libreport.
The main problem with libreport-python is that it requires 'dnf' in and
this requirement prevent us from adding libreport and
abrt-addon-coredump-helper to Atomic hosts.
Signed-off-by: Jakub Filak <jfilak@redhat.com>