Use latest stemcell on aws.
Use latest stemcell on aws.

- merging is unnecessary.

[#87994366]

cloudfoundry/cf-riak-cs-release,mikfreedman/cf-riak-cs-release,datianshi/cf-riak-cs-release,mikfreedman/cf-riak-cs-release,mikfreedman/cf-riak-cs-release,datianshi/cf-riak-cs-release,mikfreedman/cf-riak-cs-release,datianshi/cf-riak-cs-release,cloudfoundry/cf-riak-cs-release,cloudfoundry/cf-riak-cs-release,cloudfoundry/cf-riak-cs-release,datianshi/cf-riak-cs-release