storage/posix: Remove dead code in xattrop

Change-Id: I48ba81ad342e3c8fe1d81f8e57e61676dd356fb0
BUG: 1092749
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/7318
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>