Merge branch 'stable-2.15' into stable-2.16

* stable-2.15:
  EventsLogCleaner: Don't use lambda to create tasks
  Add unified prefix '[pluginName]' to both queues and task
  Upgrade bazlets to latest stable-2.15 to build with 2.15.18 API
  Upgrade bazlets to latest stable-2.15
  Upgrade bazlets to latest stable-2.14
  Bazel: Migrate workspace status script to python

Change-Id: I5a12b4d9e4bca952795868d9838056eff07590ab