cluster/afr: sync xattrs removed on source to sink(s)

xattrs are first removed from sink followed by setting
source xattrs.

Change-Id: I181cb5b785b667bbfc6e40787a2183a8f45de06b
BUG: 906646
Signed-off-by: Venky Shankar <vshankar@redhat.com>
Reviewed-on: http://review.gluster.org/4656
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>