glusterfs.spec: Add _sharedstatedir for RHEL5

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> # rpm --showrc | grep sharedstatedir | grep com
-14: _sharedstatedir %{_prefix}/com
> # cat /etc/redhat-release
Red Hat Enterprise Linux Server release 5.8 (Tikanga)
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EL5 package has a missing macro _sharedstatedir which
should be pointing to `/var/lib` not `%{_prefix}/com`

Change-Id: Ida72360d73d5dffa767c69642ee395e9c82fa8c6
BUG: 1003184
Signed-off-by: Harshavardhana <harsha@harshavardhana.net>
Reviewed-on: http://review.gluster.org/6054
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>