Use config legacy processing in Skipper (#5673)

Author: jvalkeal

spring-cloud-skipper/spring-cloud-skipper-server-core/src/main/resources/application.yml

@@ -41,6 +41,8 @@ server:
 spring:
   main:
     banner-mode: "off"
+  config:
+    use-legacy-processing: true
   data:
     rest:
       base-path: /api