Upgrade bazlets to latest stable-2.15 to build with 2.15.11 API
Upgrade bazlets to latest stable-2.15 to build with 2.15.11 API

Change-Id: I5e3de5cbba9eb487cad762ff63586179826b4e91

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