AWS::SQS::Queue - use OpenSSL for Digest needs

As with #529 (https://github.com/aws/aws-sdk-ruby/commit/ee75b781dac33fae825b2f652d8aa6234b6ddf59), I would like for `AWS::SQS::Queue` to switch to using `OpenSSL::Digest` instead of `Digest`. Without this change I am running into `Digest::Base cannot be directly inherited in Ruby` when running multiple MRI threads.