glusterd: use gf_strdup() in place of strdup()

Change-Id: Idee71019dbc6eeaa0a808d671b29d6f3038a1a89
BUG: 913487
Signed-off-by: Krutika Dhananjay <kdhananj@redhat.com>
Reviewed-on: http://review.gluster.org/4563
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>