Disallow creating buckets even with different domains (#8716)

If two distinct clusters are started with different domains
along with single common domain, this situation was leading
to conflicting buckets getting created on different clusters

To avoid this do not prematurely error out if the key has no
entries, let the caller decide on which entry matches and
which entry is valid. This allows support for MINIO_DOMAIN
with one common domain, but each cluster may have their own
domains.

Fixes #8705

cmd/config/etcd/dns/etcd_dns.go

@@ -117,9 +117,6 @@ func (c *CoreDNS) list(key string) ([]SrvRecord, error) {
 		if err != nil {
 			return nil, err
 		}
-		if r.Count == 0 {
-			return nil, ErrNoEntriesFound
-		}
 	}
 
 	var srvRecords []SrvRecord
@@ -143,9 +140,6 @@ func (c *CoreDNS) list(key string) ([]SrvRecord, error) {
 		srvRecords = append(srvRecords, srvRecord)
 
 	}
-	if len(srvRecords) == 0 {
-		return nil, ErrNoEntriesFound
-	}
 	sort.Slice(srvRecords, func(i int, j int) bool {
 		return srvRecords[i].Key < srvRecords[j].Key
 	})