Address FindBugs warnings

WTF. Didn't notice that. It would be safe to compare the integer form. The String should be an integer as per: https://github.com/jclouds/jclouds-labs/blob/master/abiquo/src/main/java/org/jclouds/abiquo/compute/functions/VirtualMachineTemplateToImage.java#L62
Thanks for spotting this!