Use aws-sdk-s3 gem instead of massive aws-sdk
Backporting upstream change from https://github.com/chef/omnibus/commit/fa31aa041a71071ca85fb4719288d439de7463a6
Needed to unblock AWS AMI automation at https://gitlab.com/gitlab-org/omnibus-gitlab/issues/4046#note_155992702 .
Edited by Balasankar 'Balu' C