Update to Sonarqube 2.1-rc1

Issue gh-4052

build.gradle

@@ -14,7 +14,7 @@ buildscript {
 }
 
 plugins {
-	id "org.sonarqube" version "1.2"
+	id "org.sonarqube" version "2.1-rc1"
 }
 
 apply plugin: 'base'