filer prefer volume server in same data center (#3405)

* initial prefer same data center
https://github.com/seaweedfs/seaweedfs/issues/3404

* GetDataCenter

* prefer same data center for ReplicationSource

* GetDataCenterId

* remove glog

weed/s3api/s3api_handlers.go

@@ -26,6 +26,10 @@ func (s3a *S3ApiServer) AdjustedUrl(location *filer_pb.Location) string {
 	return location.Url
 }
 
+func (s3a *S3ApiServer) GetDataCenter() string {
+	return s3a.option.DataCenter
+}
+
 func writeSuccessResponseXML(w http.ResponseWriter, r *http.Request, response interface{}) {
 	s3err.WriteXMLResponse(w, r, http.StatusOK, response)
 	s3err.PostLog(r, http.StatusOK, s3err.ErrNone)

weed/s3api/s3api_server.go

@@ -29,6 +29,7 @@ type S3ApiServerOption struct {
 	AllowEmptyFolder          bool
 	AllowDeleteBucketNotEmpty bool
 	LocalFilerSocket          *string
+	DataCenter                string
 }
 
 type S3ApiServer struct {