Handle S3 NotFound errors

[hoegertn]

Caused by: com.amazonaws.services.s3.model.AmazonS3Exception: Not Found (Service: Amazon S3; Status Code: 404; Error Code: 404 Not Found; Request ID: B96E574D0C85F285), S3 Extended Request ID:
at com.amazonaws.http.AmazonHttpClient.handleErrorResponse(AmazonHttpClient.java:1077)
at com.amazonaws.http.AmazonHttpClient.executeOneRequest(AmazonHttpClient.java:725)
at com.amazonaws.http.AmazonHttpClient.executeHelper(AmazonHttpClient.java:460)
at com.amazonaws.http.AmazonHttpClient.execute(AmazonHttpClient.java:295)
at com.amazonaws.services.s3.AmazonS3Client.invoke(AmazonS3Client.java:3697)
at com.amazonaws.services.s3.AmazonS3Client.getObjectMetadata(AmazonS3Client.java:999)
at com.amazonaws.services.s3.AmazonS3Client.getObjectMetadata(AmazonS3Client.java:977)
at de.cinovo.cloudconductor.server.repo.provider.AWSS3Provider.getEntry(AWSS3Provider.java:75)
at de.cinovo.cloudconductor.server.repo.RepoImpl.get(RepoImpl.java:47)
at sun.reflect.GeneratedMethodAccessor335.invoke(Unknown Source)