Compile against Gerrit 2.15.1
Compile against Gerrit 2.15.1

Change-Id: If3d925a812792498356fa5057293e383d13ca735

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