cluster/afr: Remove strict-readdir implementation

Leaving option frame-work un-changed for backward compatibility.

Change-Id: I40bce1ec360801307e67f09e53b0721f64efab37
BUG: 886998
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/4309
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>