AWS: Add EBSOptimized flag to Autoscaling Launch Configuration

Adds the EbsOptimized flag to launch configurations. See here for reference.
http://docs.aws.amazon.com/AutoScaling/latest/APIReference/API_CreateLaunchConfiguration.html 

The merge with the options hash later on should override the EbsOptimized setting... so 'false' should work here as a default.