libglusterfs: Fix compilation warning

Change-Id: Ibba7a6fd3119c85c78cb12628d85c7f9210e6b8c
BUG: 928648
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/5412
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>