Use reactor snapshots

- Reactor 3.4.0 has issue where emit my violate specs,
  thus causing issues in statemachine itself
  https://github.com/reactor/reactor-core/issues/2488
- That is now fixed in 3.4.1 snapshots so force build
  to use it now to wait boot 2.4.1.

build.gradle

@@ -88,6 +88,7 @@ configure(allprojects) {
 	dependencyManagement {
 		imports {
 			mavenBom "org.springframework.boot:spring-boot-dependencies:$springBootVersion"
+			mavenBom "io.projectreactor:reactor-bom:2020.0.2-SNAPSHOT"
 		}
 		dependencies {
 			dependency "log4j:log4j:$log4jVersion"