RPM packaging: don't include foreign-scm-helper bits yet

The files in /usr/lib/python* are only the support infrastructure for
foreign scm interface yet to be written and/or shipped with git.  Don't
include them in the binary package (this will also free us from Python
dependency).

When we ship with foreign scm interface, we will need to package these
files with it in a separate subpackage, but we are not there yet.

Signed-off-by: Junio C Hamano <gitster@pobox.com>