Merge branch 'stable-2.15' into stable-2.16

* stable-2.15:
  Upgrade bazlets to latest stable-2.15
  Upgrade bazlets to latest stable-2.14
  Update bazlets to fix build with bazel 0.23
  Update bazlets to fix build with bazel 0.23

Change-Id: I1ab80fbcec8f6c6f61192c60d39c7d40c3bc0611