fix Elasticsearch 1.2.1 log path parsing

hello

I noticed I couldn't find the logs after installing Elasticsearch 1.2.1  This fixes the parsing in config.  Please review.  Thank you.

[1.2.1 config file (github)](https://github.com/elasticsearch/elasticsearch/blob/6c95b759f9e7ef0f8e17f77d850da43ce8a4b364/config/elasticsearch.yml#L155-L167)
:+1: 

@mikemcquaid The default value is just `logs` relative to the installed directory (`/usr/local/Cellar/elasticsearch/1.2.1/logs/`) which is not desired.