Use FQDN for GCE metadata endpoint. (#7520)

Closes #7517.

Author: rsalmond

google/cloud/logging/_helpers.py

@@ -21,7 +21,7 @@
 from google.cloud.logging.entries import StructEntry
 from google.cloud.logging.entries import TextEntry
 
-METADATA_URL = "http://metadata/computeMetadata/v1/"
+METADATA_URL = "http://metadata.google.internal./computeMetadata/v1/"
 METADATA_HEADERS = {"Metadata-Flavor": "Google"}