Upgrade bazlets to latest stable-2.15

- download_file.py: Synchronize curl options with gerrit core

Change-Id: Ic57b35e489a4a95a2e8a259741c79d38ba657047
diff --git a/WORKSPACE b/WORKSPACE
index a6d71d7..f49ed12 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -3,7 +3,7 @@
 load("//:bazlets.bzl", "load_bazlets")
 
 load_bazlets(
-    commit = "92f6cad246b41c5b2f9464ecbd4b7c635015319f",
+    commit = "d60efafe2fa2581d8b6f10aeb80beef5a77b8093",
     #local_path = "/home/<user>/projects/bazlets",
 )