Fixes to Grails manual configuration sample

 1. Added import statement for clarity
 2. Use `.cloud` instead of `.getCloud()` cause it's groovier.
 3. Removed second argument to `cloud.getServiceInfo()` as [Cloud](https://github.com/spring-projects/spring-cloud/blob/master/core/src/main/java/org/springframework/cloud/Cloud.java#L75) does not seem to have a two argument `getServiceInfo` method.
 4. Switch `url` (which doesn't exist) to `jdbcUrl` which is what [RelationalServiceInfo](https://github.com/spring-projects/spring-cloud/blob/master/core/src/main/java/org/springframework/cloud/service/common/RelationalServiceInfo.java) makes available.