Add missing returns to the Historical API handlers
Add missing returns to the Historical API handlers

The historical API handlers were missing return statements after
`response.WriteError` calls in a couple of places.  This does not
prevent it from functioning currently, but with #1252, it causes
issues.

bruceauyeung/heapster,aegixx/heapster,adfin/statster,piosz/heapster,krzyzacy/heapster,Stackdriver/heapster,jackzampolin/heapster,saiwl/heapster,taimir/heapster,bruceauyeung/heapster,aegixx/heapster,krzyzacy/heapster,luxas/heapster,johanneswuerbach/heapster,andyxning/heapster,burmanm/heapster,mwringe/heapster,adfin/statster,taimir/heapster,mwringe/heapster,luxas/heapster,whuwxl/heapster,bluebreezecf/heapster,AlmogBaku/heapster,AlmogBaku/heapster,burmanm/heapster,saiwl/heapster,Stackdriver/heapster,liubog2008/heapster,bluebreezecf/heapster,whuwxl/heapster,huangyuqi/heapster,johanneswuerbach/heapster,liubog2008/heapster,jackzampolin/heapster,andyxning/heapster,piosz/heapster,huangyuqi/heapster