cluster/afr: Fix dirent leak

afr does itransform by taking the list of entries given by client xlator
to separate list but doesn't free that list.

Change-Id: Ibb4d38b4934b2bb924385c88f9d7942fad933cb9
BUG: 1117243
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/8261
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Krutika Dhananjay <kdhananj@redhat.com>
Reviewed-by: Ravishankar N <ravishankar@redhat.com>