Merge branch 'stable-2.15' into stable-2.16

* stable-2.15:
  Update mockito-core to 2.24.0
  Upgrade bazlets to latest stable-2.15 to build with 2.15.9 API
  Upgrade bazlets to latest stable-2.15 to build with 2.15.8 API
  Upgrade bazlets to latest stable-2.14 to build with 2.14.18 API

Change-Id: I5ff6f30a0eec21ad4973427fb374c7774b99c755