make stripMapping default to true to not change the current functionality

spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/zuul/ZuulProxyProperties.java

@@ -10,5 +10,5 @@ import org.springframework.boot.context.properties.ConfigurationProperties;
 @ConfigurationProperties("zuul.proxy")
 public class ZuulProxyProperties {
     private String mapping = "/proxy";
-    private boolean stripMapping = false;
+    private boolean stripMapping = true; // this is currently the default behaviour
 }

spring-cloud-netflix-core/src/test/resources/application.yml

@@ -10,6 +10,7 @@ eureka:
 zuul:
   proxy:
     mapping: /api
+    stripMapping: false
     route:
       testclient: /api/testing123
       stores: /api/stores