FIX: Amazon

- Properly terminate the instances that should halt
- use try/except clause for the connection, as the S_OK S_ERROR are no
use in constructors
FIX: no need to pass a list of UniqueIDs 

The list is created if needed.
FIX: the stopInstances must return standard structure

Also catch any exception and return it in S_ERROR
Fix: cloud driver name
fix Amazon instead of amazon
Because of lower case, Amazon must remain amazon
cloudDriver MUST be lower case at it comes from the MonitorAgent that
uses lower case.
Merge pull request #74 from sposs/fixAmazonBis

FIX: Amazon