EUCA-5425:error codes for all ELB operations
 -- whenever there's AWS-defined error codes (http status code) and message, we follow the same convention
 -- Internal failure returns http status 400 so that the client does not repeat the operation
Merge branch 'testing' into dev/spark/services
EUCA-5963: cloudwatch healthy/unhealthy host count fix for elb
Merge branch 'dev/spark/services' into testing