Merge branch 'stable-2.15'

* 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: Ia5c06de82236b2c5ee5ee86bf194a055928c2c70