Added possibility to switch from index to ip in graphite key generation

The index used in graphite keys is not working in multi AZ setups. In this case the job from z1 with the same index as the job in z2 will both log into the same graphite key. 

I extended the get_metrics_name to use the IP instead. To be compatible to older versions this change is disabled by default. It can be enabled though property (graphite.ip_key=true) I will file a pull request for cf-release if this change will make it into the collector.

Cheers
Johannes