Merge branch 'stable-2.15' into stable-2.16

* stable-2.15:
  Upgrade bazlets to latest stable-2.15 to build with 2.15.12 API
  Upgrade bazlets to latest stable-2.14 to build with 2.14.19 API

Change-Id: I9d5c50e9f6f160caf4ff88b9c92d58c99868f8bb