cluster/afr: skip directory inspection when entry self-heal is off

When user has explicitly configured to disable entry self-heal in the
client, it is wrong to do the healing in opendir. So skip it. This
is especially useful to reduce opendir() times after graph switches.

Change-Id: Ic6eb9ff2334a5b8417f2f35410a366a536bad5df
Signed-off-by: Anand Avati <avati@redhat.com>
Reviewed-on: http://review.gluster.org/5528
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>