Update to td-agent 3.2.0
Currently we've pinned version 3.1.1 because the newer one doesn't seem to process anything. See https://github.com/fluent/fluentd-docs/issues/515#issuecomment-397936092
Currently we've pinned version 3.1.1 because the newer one doesn't seem to process anything. See https://github.com/fluent/fluentd-docs/issues/515#issuecomment-397936092