Fix InstanceExists Waiter
Fix InstanceExists Waiter

Instead of checking just the status of DescribeInstances operation from aws, we should check if the reservation have length > 0.

aws/aws-sdk-ruby,aws/aws-sdk-ruby,cjyclaire/aws-sdk-ruby,takeyuweb/aws-sdk-ruby,cjyclaire/aws-sdk-ruby,llooker/aws-sdk-ruby,hamadata/aws-sdk-ruby,hamadata/aws-sdk-ruby,takeyuweb/aws-sdk-ruby,llooker/aws-sdk-ruby,aws/aws-sdk-ruby,cjyclaire/aws-sdk-ruby,hamadata/aws-sdk-ruby,llooker/aws-sdk-ruby,takeyuweb/aws-sdk-ruby