Set default stage to 'test' in request builder

Author: mattcorey

aws-serverless-java-container-core/src/main/java/com/amazonaws/serverless/proxy/internal/testutils/AwsProxyRequestBuilder.java

@@ -53,6 +53,7 @@ public AwsProxyRequestBuilder(String path, String httpMethod) {
         this.request.setPath(path);
         this.request.setQueryStringParameters(new HashMap<>());
         this.request.setRequestContext(new ApiGatewayRequestContext());
+        this.request.getRequestContext().setStage("test");
         ApiGatewayRequestIdentity identity = new ApiGatewayRequestIdentity();
         identity.setSourceIp("127.0.0.1");
         this.request.getRequestContext().setIdentity(identity);