mgmt/glusterd: Fix wrong usage of snprintf

Change-Id: I7db752390bb742fb9f6cacce84563ff782ae352b
BUG: 1087677
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/7608
Reviewed-by: Sachin Pandit <spandit@redhat.com>
Reviewed-by: Krishnan Parthasarathi <kparthas@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Tested-by: Vijay Bellur <vbellur@redhat.com>