bump bosh_deployer gems - use fixed aws-sdk gem that can be installed

aws-sdk 1.8.1 cannot be installed due to 
https://github.com/aws/aws-sdk-ruby/pull/142; so forcing install of 1.8.1.1
which includes the fix. The ~> 1.8.0 gem dependency does not pick up 1.8.1.1
gem sadly.