fix: Use actual hostname instead of the one provided by the Spring Cloud (#1434)

Signed-off-by: Jakub Balhar <jakub@balhar.net>

Author: balhar-jakub

gateway-service/src/main/java/org/zowe/apiml/gateway/config/GatewayConfig.java

@@ -128,7 +128,7 @@ private String getProperty(String property) {
     }
 
     public static String getInstanceId(PropertyResolver resolver) {
-        String hostname = resolver.getProperty("spring.cloud.client.hostname");
+        String hostname = resolver.getProperty("apiml.service.hostname");
         String appName = resolver.getProperty("spring.application.name");
 
         String namePart = IdUtils.combineParts(hostname, SEPARATOR, appName);