Include original error backtrace in when re-raising SocketError
Include original error backtrace in when re-raising SocketError

- This should make it easier to debug what caused the original
  SocketError

[#116382509](https://www.pivotaltracker.com/story/show/116382509)

cloudfoundry-incubator/bosh-aws-cpi-release,cloudfoundry-incubator/bosh-aws-cpi-release,cloudfoundry-incubator/bosh-aws-cpi-release