Merge branch 'stable-2.15' into stable-2.16

* stable-2.15:
  Upgrade bazlets to latest stable-2.15 to build with 2.15.7 API
  Upgrade bazlets to latest stable-2.14 to build with 2.14.17 API

Change-Id: I37f737dc66e4984ae55fbb4052c498edb4754721