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

        Backport of: http://review.gluster.org/#/c/9020

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: I0bc92978efc0741d6e3f2439540d008e31472313
BUG: 1136821
Signed-off-by: Krutika Dhananjay <kdhananj@redhat.com>
Reviewed-on: http://review.gluster.org/9030
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
Tested-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Tested-by: Vijay Bellur <vbellur@redhat.com>