Update to Reactor 2020.0.15

Closes gh-607

gradle/dependency-management.gradle

@@ -7,7 +7,7 @@ if (!project.hasProperty("springSecurityVersion")) {
 }
 
 if (!project.hasProperty("reactorVersion")) {
-	ext.reactorVersion = "2020.0.13"
+	ext.reactorVersion = "2020.0.15"
 }
 
 if (!project.hasProperty("locksDisabled")) {