[ML] improve model downloader robustness (#97274)

use the resolver from ModelLoaderUtils, fix problems finding the vocabulary file

Author: Hendrik Muhs

docs/changelog/97274.yaml

@@ -0,0 +1,5 @@
+pr: 97274
+summary: Improve model downloader robustness
+area: Machine Learning
+type: bug
+issues: []

x-pack/plugin/ml-package-loader/src/main/java/org/elasticsearch/xpack/ml/packageloader/action/TransportLoadTrainedModelPackage.java

@@ -92,13 +92,13 @@ protected void masterOperation(Task task, Request request, ClusterState state, A
  final long relativeStartNanos = System.nanoTime();
  logAndWriteNotificationAtInfo(modelId, "starting model upload");
 
- URI uri = new URI(repository).resolve(packagedModelId + ModelLoaderUtils.MODEL_FILE_EXTENSION);
+ URI uri = ModelLoaderUtils.resolvePackageLocation(repository, packagedModelId + ModelLoaderUtils.MODEL_FILE_EXTENSION);
 
  // Uploading other artefacts of the model first, that way the model is last and a simple search can be used to check if the
  // download is complete
  if (Strings.isNullOrEmpty(modelPackageConfig.getVocabularyFile()) == false) {
  Tuple<List<String>, List<String>> vocabularyAndMerges = ModelLoaderUtils.loadVocabulary(
- new URI(repository).resolve(modelPackageConfig.getVocabularyFile())
+ ModelLoaderUtils.resolvePackageLocation(repository, modelPackageConfig.getVocabularyFile())
  );
 
  PutTrainedModelVocabularyAction.Request r2 = new PutTrainedModelVocabularyAction.Request(