Upgrade bazlets to latest stable-2.15 to build with 2.15.19 API
Upgrade bazlets to latest stable-2.15 to build with 2.15.19 API

Change-Id: I9591da3343d23420ee92796d9463843d7ad60f42

GerritCodeReview/plugins_javamelody,GerritCodeReview/plugins_javamelody,GerritCodeReview/plugins_javamelody