plugins/vmimage: Avoid network calls when listing cached images

In list_downloaded_images(), prevent unnecessary network calls by
setting provider._best_version from metadata after creating the
provider, and using metadata values directly instead of provider
properties which may trigger network lookups.

This fixes cascading failures where listing cached non-Fedora images
would trigger network calls to Fedora servers.

Reference: avocado-framework#6266
Assisted-By: Cursor-Claude-4-Sonnet
Signed-off-by: Harvey Lynden <hlynden@redhat.com>

Author: harvey0100

avocado/plugins/vmimage.py

@@ -40,14 +40,19 @@ def list_downloaded_images():
                                         metadata["build"],
                                         metadata["arch"],
                                     )
+                                    # Set _best_version to prevent network calls
+                                    # when accessing provider.version or file_name
+                                    provider._best_version = metadata["version"]
                                     break
                             if provider is not None:
                                 for image in files:
                                     if re.match(provider.file_name, image):
+                                        # Use metadata values directly to avoid
+                                        # network calls from provider.version property
                                         data = {
                                             "name": provider.name,
-                                            "version": provider.version,
-                                            "arch": provider.arch,
+                                            "version": metadata["version"],
+                                            "arch": metadata["arch"],
                                             "file": os.path.join(root, image),
                                         }
                                         images.append(data)