cluster/afr: Perform post-op in entry selfheal inside locks

Take entrylks in xlator domain before doing post-op (undo-pending) in
entry self-heal. This is to prevent a parallel name self-heal on
an entry under @fd->inode from reading pending xattrs while it is
being modified by SHD after entry sh below, given that
name self-heal takes locks ONLY in xlator domain and is free to read
pending changelog in the absence of the following locking.

Change-Id: Ie083ceab10155c460447f04bdce7688480f1ac4f
BUG: 1128721
Signed-off-by: Krutika Dhananjay <kdhananj@redhat.com>
Reviewed-on: http://review.gluster.org/9020
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
Tested-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>