cluster/afr: Add afr-v1 xattr compatibility

        Backport of http://review.gluster.org/8536

All the special cases v1 handles and also
self-accusing pending changelog from v1 pre-op also is handled
in this patch.

BUG: 1155017
Change-Id: I86cf6b80492be5c1f240c74f91a0e1b0dd9b58b2
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/8956
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>