Add support for CopyObject across regions and multiple Minio IPs

This PR adds CopyObject support for objects residing in buckets
in different Minio instances (where Minio instances are part of
a federated setup).

Also, added support for multiple Minio domain IPs. This is required
for distributed deployments, where one deployment may have multiple
nodes, each with a different public IP.

pkg/dns/dns.go

@@ -60,6 +60,6 @@ type SrvRecord struct {
 type Config interface {
 	Put(key string) error
 	List() ([]SrvRecord, error)
-	Get(key string) (SrvRecord, error)
+	Get(key string) ([]SrvRecord, error)
 	Delete(key string) error
 }