Map internal S3 image state to EC2 API values

Fixes the EC2 API so it maps internal S3 image state values to
ones defined by the EC2 API rather than returning the internally
used values.

Fixes bug #1074904

Change-Id: Iabbda0e5fcbe4d572c76367c6f98d4bece050e73
Merge "Map internal S3 image state to EC2 API values"