If grpc starts with `--resolver-prefix`, its memberlist will return all
alive proxy nodes. When one GRPC proxy node goes down it shouldn't
return that node, however, it's returned.
Backport of PR #15907 / commit ecfed91e5050431385961573e5c09658a66a59d5.
Co-authored-by: yellowzf <zzhf3311@163.com>
Signed-off-by: Ivan Valdes <ivan@vald.es>