Ingesters get network errors when writing dynamo data during shutdown

[jml]

time="2016-10-10T13:17:29Z" level=error msg="Failed to flush chunks for series: RequestError: send request failed\ncaused by: Put https://weaveworks-prod-chunks.s3.amazonaws.com/2/17142991289174007630%3A1476104540889%3A1476105230889: dial tcp: lookup weaveworks-prod-chunks.s3.amazonaws.com on 10.0.0.10:53: dial udp 10.0.0.10:53: connect: network is unreachable" source="cortex.go:440"

This might be a cause of data loss.

[tomwilkie]

Waiting on loggly to come back before we close this.

[tomwilkie]

K8s 1.4 upgrade seems to have fixed this (no occurrences in the log)