rpm: correct AutoRequires filtering on recent Fedora

Recent Fedora releases (F17 and newer) do not need the
__requires_exclude macro for filtering automatically generated Requires
for <xlator>.so files anymore. It is already sufficient to filter each
<xlator>.so from the Provides.

This prevents the following (harmless) warning from being printed during
build:

    Ignoring invalid regex -P ^(?!lib).*.so.*$

BUG: 972465
Change-Id: Icc36f421d283ddb993c8f31e0dfdaa4f27135bb7
Signed-off-by: Niels de Vos <ndevos@redhat.com>
Reviewed-on: http://review.gluster.org/5203
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>