Minor corrections for correcting some inconsistencies in ec2.json

Hi,
  I'm trying to write an SDK based on definitions from the JSON files.

  I've detected some inconsistencies that I'm pushing back:
   -  Renamed LaunchSpecification for SpotInstances call: There is another LaunchSpecification shape with the same name, but different definition
   - Monitoring attribute for SpotInstances is a structure, but like all structures, didn't have a shape_name

Best Regads,

Jose Luis