gfapi: Change lookup logic for "/.." and "/." .

We should handle /.. and /. in unique way,
otherwise we may end up setting glusterfs xattrs
on parent of the brick dir.

Change-Id: I206bb1751622bd912bc678fd52f4eddfd9b907c8
BUG: 1128648
Signed-off-by: Raghavendra Talur <rtalur@redhat.com>
Reviewed-on: http://review.gluster.org/8455
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>