build: only install geo-rep scripts when enabled

When geo-replication is not enabled, the related scripts should not get
installed. EPEL-5 does not support geo-replication, and the installed
but unpackaged scripts cause rebuilding for .el5 to fail.

BUG: 1169005
Change-Id: I1b6a352b73bd1ed1c5b330f54e26e81aed9a5a4e
Reported-by: Lalatendu Mohanty <lmohanty@redhat.com>
Signed-off-by: Niels de Vos <ndevos@redhat.com>
Reviewed-on: http://review.gluster.org/9221
Reviewed-by: Humble Devassy Chirammal <humble.devassy@gmail.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>