added partial test coverage - added coverage for download file name to be   persisted into the transfer handle - did not add coverage for the VersionID within   RetryDownload(); the existing test harness   specifically disabled testing of versions
added partial test coverage
- added coverage for download file name to be
  persisted into the transfer handle
- did not add coverage for the VersionID within
  RetryDownload(); the existing test harness
  specifically disabled testing of versions

jt70471/aws-sdk-cpp,JoyIfBam5/aws-sdk-cpp,cedral/aws-sdk-cpp,JoyIfBam5/aws-sdk-cpp,JoyIfBam5/aws-sdk-cpp,JoyIfBam5/aws-sdk-cpp,aws/aws-sdk-cpp,jt70471/aws-sdk-cpp,jt70471/aws-sdk-cpp,awslabs/aws-sdk-cpp,cedral/aws-sdk-cpp,JoyIfBam5/aws-sdk-cpp,aws/aws-sdk-cpp,jt70471/aws-sdk-cpp,cedral/aws-sdk-cpp,awslabs/aws-sdk-cpp,awslabs/aws-sdk-cpp,awslabs/aws-sdk-cpp,cedral/aws-sdk-cpp,JoyIfBam5/aws-sdk-cpp,aws/aws-sdk-cpp,jt70471/aws-sdk-cpp,aws/aws-sdk-cpp,cedral/aws-sdk-cpp,aws/aws-sdk-cpp,jt70471/aws-sdk-cpp,aws/aws-sdk-cpp,cedral/aws-sdk-cpp