plugin/etcd: Stop target stripping at the end of a name (#8584)

Stops stripping when the next-label operation reaches the end sentinel in DNS

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

plugin/etcd/msg/service.go

@@ -165,6 +165,9 @@ func targetStrip(name string, targetStrip int) string {
 	offset, end := 0, false
 	for range targetStrip {
 		offset, end = dns.NextLabel(name, offset)
+		if end {
+			break
+		}
 	}
 	if end {
 		// We overshot the name, use the original one.