Move VolumeAttachment updates to Cinder resource

According to AWS docs AWS::EC2::VolumeAttachment resource does not
support any updates [1]. Support of updates in our AWS-compatible
resource is a bug and needs to be fixed without deprecation period.

This patch moves VolumeAttachment update logic to native Cinder
resource.

[1] http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-ec2-ebs-volumeattachment.html

Change-Id: I54d302dbec66ddd49c4a774376df99e7e9d63980
Partial-Bug: #1340096