Improve metadata URL parsing

Signed-off-by: Teodora Sechkova <tsechkova@vmware.com>

tests/repository_simulator.py

@@ -199,11 +199,11 @@ def fetch(self, url: str) -> Iterator[bytes]:
         if path.startswith("/metadata/") and path.endswith(".json"):
             # figure out rolename and version
             ver_and_name = path[len("/metadata/") :][: -len(".json")]
+            version, _, role = ver_and_name.partition(".")
             # root is always version-prefixed while timestamp is always NOT
-            if ver_and_name.endswith("root") or (
+            if role == "root" or (
                 self.root.consistent_snapshot and ver_and_name != "timestamp"
             ):
-                version, _, role = ver_and_name.partition(".")
                 version = int(version)
             else:
                 # the file is not version-prefixed