Avoid xattr printed out as HTTP headers

fix https://github.com/chrislusf/seaweedfs/issues/2336

weed/server/filer_server_handlers_read.go

@@ -97,7 +97,10 @@ func (fs *FilerServer) GetOrHeadHandler(w http.ResponseWriter, r *http.Request)
 
 	// print out the header from extended properties
 	for k, v := range entry.Extended {
-		w.Header().Set(k, string(v))
+		if !strings.HasPrefix(k, "xattr-") {
+			// "xattr-" prefix is set in filesys.XATTR_PREFIX
+			w.Header().Set(k, string(v))
+		}
 	}
 
 	//Seaweed custom header are not visible to Vue or javascript