storage/posix: Fix open-fd-count virtual xattr

Send open-fd-count maintained in inode.

Change-Id: I23db5d052bdeb4f67978ff618ed5a0bed7d1592d
BUG: 908146
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/4469
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>