Update bazlets to latest stable-2.15 to build with 2.15.4 API
Update bazlets to latest stable-2.15 to build with 2.15.4 API

Change-Id: Ibb9223efff73a80f21b46351e74105002f7e3217

GerritCodeReview/plugins_admin-console,GerritCodeReview/plugins_admin-console,GerritCodeReview/plugins_admin-console