Improve error handling when sending data to Riemann
Improve error handling when sending data to Riemann

It set to nil the client, what provoked panics, now
it tries to send all events, just in case the errors
are not connection related and then it forces a
reconnection.

More information logged when sending data.

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