Upgrade bazlets to latest stable-2.15
Upgrade bazlets to latest stable-2.15

Includes further fixes for --incompatible_disallow_legacy_java_provider.

Change-Id: Ibece8324414affb6442a39caf9dcec1d7a37f4c0

GerritCodeReview/plugins_delete-project,GerritCodeReview/plugins_delete-project,GerritCodeReview/plugins_delete-project,GerritCodeReview/plugins_delete-project